diff --git a/.github/workflows/napi4.yaml b/.github/workflows/napi3.yaml
similarity index 83%
rename from .github/workflows/napi4.yaml
rename to .github/workflows/napi3.yaml
index c06475a1..1cc3afc4 100644
--- a/.github/workflows/napi4.yaml
+++ b/.github/workflows/napi3.yaml
@@ -1,19 +1,20 @@
-name: Linux-NAPI4
+name: Linux-N-API-3
 
 on: [push, pull_request]
 
 jobs:
   build_and_test:
-    name: stable - x86_64-unknown-linux-gnu - node@12.10
+    name: stable - x86_64-unknown-linux-gnu - node@10.0
     runs-on: ubuntu-latest
 
     steps:
       - uses: actions/checkout@v2
 
       - name: Setup node
-        uses: actions/setup-node@v1
-        with:
-          node-version: 12.10
+        run: |
+          wget https://nodejs.org/dist/v10.0.0/node-v10.0.0-linux-x64.tar.xz
+          tar xf node-v10.0.0-linux-x64.tar.xz
+          echo "::add-path::$(pwd)/node-v10.0.0-linux-x64/bin"
 
       - name: Install stable
         uses: actions-rs/toolchain@v1
@@ -57,7 +58,7 @@ jobs:
 
       - name: Unit tests
         run: |
-          yarn --ignore-engines
+          yarn add ava@2 --dev --ignore-engines
           yarn --cwd ./test_module build
           yarn test
         env:
diff --git a/.github/workflows/windows.yaml b/.github/workflows/windows.yaml
index b6fd81dd..1b2edc67 100644
--- a/.github/workflows/windows.yaml
+++ b/.github/workflows/windows.yaml
@@ -30,7 +30,7 @@ jobs:
       - name: Install llvm
         run: choco install -y llvm
       - name: set environment variables
-        uses: allenevans/set-env@v1.0.0
+        uses: allenevans/set-env@v1.1.0
         with:
           LIBCLANG_PATH: 'C:\Program Files\LLVM\bin'
       - name: Generate Cargo.lock
diff --git a/build/src/lib.rs b/build/src/lib.rs
index de75193d..5f18b121 100644
--- a/build/src/lib.rs
+++ b/build/src/lib.rs
@@ -83,14 +83,14 @@ fn setup_napi_feature() {
 
   let napi_version_number = napi_version.trim().parse::<u32>().unwrap();
 
-  if napi_version_number < 4 {
+  if napi_version_number < 2 {
     panic!("current napi version is too low");
   }
 
-  if napi_version_number == 4 {
+  if napi_version_number == 2 {
     println!("cargo:rustc-cfg=napi{}", napi_version_number);
   } else {
-    for version in 4..napi_version_number {
+    for version in 2..(napi_version_number + 1) {
       println!("cargo:rustc-cfg=napi{}", version);
     }
   }
diff --git a/napi/Cargo.toml b/napi/Cargo.toml
index a9c967d4..365064a6 100644
--- a/napi/Cargo.toml
+++ b/napi/Cargo.toml
@@ -9,6 +9,12 @@ repository = "https://github.com/Brooooooklyn/napi-rs"
 keywords = ["NodeJS", "FFI", "NAPI", "n-api"]
 edition = "2018"
 
+[features]
+libuv = ["futures"]
+
+[dependencies]
+futures = { version = "0.3", optional = true }
+
 [target.'cfg(windows)'.build-dependencies]
 flate2 = "1.0"
 reqwest = { version = "0.10", features = ["native-tls", "blocking"] }
diff --git a/napi/src/env.rs b/napi/src/env.rs
index 4c5b1be1..14047573 100644
--- a/napi/src/env.rs
+++ b/napi/src/env.rs
@@ -10,16 +10,25 @@ use crate::error::check_status;
 use crate::js_values::*;
 use crate::{sys, AsyncWork, Error, NodeVersion, Result, Status};
 
+#[cfg(all(feature = "libuv", napi4))]
+use crate::promise;
+#[cfg(all(feature = "libuv", napi4))]
+use crate::uv;
+#[cfg(all(feature = "libuv", napi4))]
+use std::future::Future;
+
 pub type Callback = extern "C" fn(sys::napi_env, sys::napi_callback_info) -> sys::napi_value;
 
 #[derive(Clone, Copy, Debug)]
 pub struct Env(pub(crate) sys::napi_env);
 
 impl Env {
+  #[inline]
   pub fn from_raw(env: sys::napi_env) -> Self {
     Env(env)
   }
 
+  #[inline]
   pub fn get_undefined(&self) -> Result<JsUndefined> {
     let mut raw_value = ptr::null_mut();
     let status = unsafe { sys::napi_get_undefined(self.0, &mut raw_value) };
@@ -27,6 +36,7 @@ impl Env {
     Ok(JsUndefined::from_raw_unchecked(self.0, raw_value))
   }
 
+  #[inline]
   pub fn get_null(&self) -> Result<JsNull> {
     let mut raw_value = ptr::null_mut();
     let status = unsafe { sys::napi_get_null(self.0, &mut raw_value) };
@@ -34,6 +44,7 @@ impl Env {
     Ok(JsNull::from_raw_unchecked(self.0, raw_value))
   }
 
+  #[inline]
   pub fn get_boolean(&self, value: bool) -> Result<JsBoolean> {
     let mut raw_value = ptr::null_mut();
     let status = unsafe { sys::napi_get_boolean(self.0, value, &mut raw_value) };
@@ -41,6 +52,7 @@ impl Env {
     Ok(JsBoolean::from_raw_unchecked(self.0, raw_value))
   }
 
+  #[inline]
   pub fn create_int32(&self, int: i32) -> Result<JsNumber> {
     let mut raw_value = ptr::null_mut();
     let status =
@@ -49,6 +61,7 @@ impl Env {
     Ok(JsNumber::from_raw_unchecked(self.0, raw_value))
   }
 
+  #[inline]
   pub fn create_int64(&self, int: i64) -> Result<JsNumber> {
     let mut raw_value = ptr::null_mut();
     let status =
@@ -57,6 +70,7 @@ impl Env {
     Ok(JsNumber::from_raw_unchecked(self.0, raw_value))
   }
 
+  #[inline]
   pub fn create_uint32(&self, number: u32) -> Result<JsNumber> {
     let mut raw_value = ptr::null_mut();
     let status = unsafe { sys::napi_create_uint32(self.0, number, &mut raw_value) };
@@ -64,6 +78,7 @@ impl Env {
     Ok(JsNumber::from_raw_unchecked(self.0, raw_value))
   }
 
+  #[inline]
   pub fn create_double(&self, double: f64) -> Result<JsNumber> {
     let mut raw_value = ptr::null_mut();
     let status =
@@ -72,20 +87,35 @@ impl Env {
     Ok(JsNumber::from_raw_unchecked(self.0, raw_value))
   }
 
+  #[inline]
   pub fn create_string(&self, s: &str) -> Result<JsString> {
+    self.create_string_from_chars(s.as_ptr() as *const _, s.len() as u64)
+  }
+
+  #[inline]
+  pub fn create_string_from_std(&self, s: String) -> Result<JsString> {
+    self.create_string_from_chars(s.as_ptr() as *const _, s.len() as u64)
+  }
+
+  #[inline]
+  pub fn create_string_from_vec_u8(&self, bytes: Vec<u8>) -> Result<JsString> {
+    self.create_string_from_chars(bytes.as_ptr() as *const _, bytes.len() as u64)
+  }
+
+  #[inline]
+  pub fn create_string_from_vec_i8(&self, bytes: Vec<i8>) -> Result<JsString> {
+    self.create_string_from_chars(bytes.as_ptr(), bytes.len() as u64)
+  }
+
+  #[inline]
+  fn create_string_from_chars(&self, data_ptr: *const c_char, len: u64) -> Result<JsString> {
     let mut raw_value = ptr::null_mut();
-    let status = unsafe {
-      sys::napi_create_string_utf8(
-        self.0,
-        s.as_ptr() as *const c_char,
-        s.len() as u64,
-        &mut raw_value,
-      )
-    };
+    let status = unsafe { sys::napi_create_string_utf8(self.0, data_ptr, len, &mut raw_value) };
     check_status(status)?;
     Ok(JsString::from_raw_unchecked(self.0, raw_value))
   }
 
+  #[inline]
   pub fn create_string_utf16(&self, chars: &[u16]) -> Result<JsString> {
     let mut raw_value = ptr::null_mut();
     let status = unsafe {
@@ -95,12 +125,14 @@ impl Env {
     Ok(JsString::from_raw_unchecked(self.0, raw_value))
   }
 
+  #[inline]
   pub fn create_symbol_from_js_string(&self, description: JsString) -> Result<JsSymbol> {
     let mut result = ptr::null_mut();
     check_status(unsafe { sys::napi_create_symbol(self.0, description.0.value, &mut result) })?;
     Ok(JsSymbol::from_raw_unchecked(self.0, result))
   }
 
+  #[inline]
   pub fn create_symbol(&self, description: Option<&str>) -> Result<JsSymbol> {
     let mut result = ptr::null_mut();
     check_status(unsafe {
@@ -116,6 +148,7 @@ impl Env {
     Ok(JsSymbol::from_raw_unchecked(self.0, result))
   }
 
+  #[inline]
   pub fn create_object(&self) -> Result<JsObject> {
     let mut raw_value = ptr::null_mut();
     let status = unsafe { sys::napi_create_object(self.0, &mut raw_value) };
@@ -123,6 +156,7 @@ impl Env {
     Ok(JsObject::from_raw_unchecked(self.0, raw_value))
   }
 
+  #[inline]
   pub fn create_array_with_length(&self, length: usize) -> Result<JsObject> {
     let mut raw_value = ptr::null_mut();
     let status =
@@ -131,6 +165,7 @@ impl Env {
     Ok(JsObject::from_raw_unchecked(self.0, raw_value))
   }
 
+  #[inline]
   pub fn create_buffer(&self, length: u64) -> Result<JsBuffer> {
     let mut raw_value = ptr::null_mut();
     let mut data = Vec::with_capacity(length as usize);
@@ -145,6 +180,7 @@ impl Env {
     Ok(buffer)
   }
 
+  #[inline]
   pub fn create_buffer_with_data(&self, data: Vec<u8>) -> Result<JsBuffer> {
     let length = data.len() as u64;
     let mut raw_value = ptr::null_mut();
@@ -155,15 +191,15 @@ impl Env {
         length,
         data_ptr as *mut c_void,
         Some(drop_buffer),
-        &length as *const _ as *mut c_void,
+        Box::leak(Box::new(length)) as *mut u64 as *mut _,
         &mut raw_value,
       )
     };
     check_status(status)?;
     let mut changed = 0;
-    let ajust_external_memory_status =
+    let adjust_external_memory_status =
       unsafe { sys::napi_adjust_external_memory(self.0, length as i64, &mut changed) };
-    check_status(ajust_external_memory_status)?;
+    check_status(adjust_external_memory_status)?;
     mem::forget(data);
     let mut buffer = JsBuffer::from_raw_unchecked(self.0, raw_value);
     buffer.data = data_ptr as *const u8;
@@ -171,6 +207,7 @@ impl Env {
     Ok(buffer)
   }
 
+  #[inline]
   pub fn create_arraybuffer(&self, length: u64) -> Result<JsArrayBuffer> {
     let mut raw_value = ptr::null_mut();
     let mut data = Vec::with_capacity(length as usize);
@@ -185,6 +222,7 @@ impl Env {
     Ok(array_buffer)
   }
 
+  #[inline]
   pub fn create_arraybuffer_with_data(&self, data: Vec<u8>) -> Result<JsArrayBuffer> {
     let length = data.len() as u64;
     let mut raw_value = ptr::null_mut();
@@ -201,9 +239,9 @@ impl Env {
     };
     check_status(status)?;
     let mut changed = 0;
-    let ajust_external_memory_status =
+    let adjust_external_memory_status =
       unsafe { sys::napi_adjust_external_memory(self.0, length as i64, &mut changed) };
-    check_status(ajust_external_memory_status)?;
+    check_status(adjust_external_memory_status)?;
     mem::forget(data);
     let mut array_buffer = JsArrayBuffer::from_raw_unchecked(self.0, raw_value);
     array_buffer.data = data_ptr as *const u8;
@@ -211,6 +249,7 @@ impl Env {
     Ok(array_buffer)
   }
 
+  #[inline]
   pub fn create_function(&self, name: &str, callback: Callback) -> Result<JsFunction> {
     let mut raw_result = ptr::null_mut();
     let status = unsafe {
@@ -229,18 +268,21 @@ impl Env {
     Ok(JsFunction::from_raw_unchecked(self.0, raw_result))
   }
 
+  #[inline]
   pub fn throw(&self, error: Error) -> Result<()> {
     let err_value = self.create_error(error)?.0.value;
     check_status(unsafe { sys::napi_throw(self.0, err_value) })?;
     Ok(())
   }
 
+  #[inline]
   pub fn throw_error(&self, msg: &str) -> Result<()> {
     let status = unsafe { sys::napi_throw_error(self.0, ptr::null(), msg.as_ptr() as *const _) };
     check_status(status)?;
     Ok(())
   }
 
+  #[inline]
   pub fn create_reference<T: NapiValue>(&self, value: T) -> Result<Ref<T>> {
     let mut raw_ref = ptr::null_mut();
     let initial_ref_count = 1;
@@ -253,6 +295,7 @@ impl Env {
     Ok(Ref::new(self.0, raw_ref))
   }
 
+  #[inline]
   pub fn get_reference_value<T: NapiValue>(&self, reference: &Ref<T>) -> Result<T> {
     let mut raw_value = ptr::null_mut();
     unsafe {
@@ -263,6 +306,7 @@ impl Env {
     Ok(T::from_raw_unchecked(self.0, raw_value))
   }
 
+  #[inline]
   pub fn define_class(
     &self,
     name: &str,
@@ -293,6 +337,7 @@ impl Env {
     Ok(JsFunction::from_raw_unchecked(self.0, raw_result))
   }
 
+  #[inline]
   pub fn wrap<T: 'static>(&self, js_object: &mut JsObject, native_object: T) -> Result<()> {
     let status = unsafe {
       sys::napi_wrap(
@@ -308,6 +353,7 @@ impl Env {
     check_status(status).or(Ok(()))
   }
 
+  #[inline]
   pub fn unwrap<T: 'static>(&self, js_object: &JsObject) -> Result<&mut T> {
     unsafe {
       let mut unknown_tagged_object: *mut c_void = ptr::null_mut();
@@ -330,6 +376,7 @@ impl Env {
     }
   }
 
+  #[inline]
   pub fn drop_wrapped<T: 'static>(&self, js_object: JsObject) -> Result<()> {
     unsafe {
       let mut unknown_tagged_object: *mut c_void = ptr::null_mut();
@@ -351,6 +398,7 @@ impl Env {
     }
   }
 
+  #[inline]
   pub fn create_external<T: 'static>(&self, native_object: T) -> Result<JsExternal> {
     let mut object_value = ptr::null_mut();
     let status = unsafe {
@@ -367,6 +415,7 @@ impl Env {
     Ok(JsExternal::from_raw_unchecked(self.0, object_value))
   }
 
+  #[inline]
   pub fn get_value_external<T: 'static>(&self, js_external: &JsExternal) -> Result<&mut T> {
     unsafe {
       let mut unknown_tagged_object = ptr::null_mut();
@@ -391,6 +440,7 @@ impl Env {
     }
   }
 
+  #[inline]
   pub fn create_error(&self, e: Error) -> Result<JsObject> {
     let reason = e.reason;
     let reason_string = self.create_string(reason.as_str())?;
@@ -407,6 +457,7 @@ impl Env {
     Ok(JsObject::from_raw_unchecked(self.0, result))
   }
 
+  #[inline]
   pub fn spawn<T: 'static + Task>(&self, task: T) -> Result<JsObject> {
     let mut raw_promise = ptr::null_mut();
     let mut raw_deferred = ptr::null_mut();
@@ -416,6 +467,67 @@ impl Env {
     Ok(JsObject::from_raw_unchecked(self.0, raw_promise))
   }
 
+  #[inline]
+  pub fn get_global(&self) -> Result<JsObject> {
+    let mut raw_global = ptr::null_mut();
+    check_status(unsafe { sys::napi_get_global(self.0, &mut raw_global) })?;
+    Ok(JsObject::from_raw_unchecked(self.0, raw_global))
+  }
+
+  #[inline]
+  pub fn get_napi_version(&self) -> Result<u32> {
+    let global = self.get_global()?;
+    let process = global.get_named_property::<JsObject>("process")?;
+    let versions = process.get_named_property::<JsObject>("versions")?;
+    let napi_version = versions.get_named_property::<JsString>("napi")?;
+    napi_version
+      .as_str()?
+      .parse()
+      .map_err(|e| Error::new(Status::InvalidArg, format!("{}", e)))
+  }
+
+  #[cfg(all(feature = "libuv", napi4))]
+  #[inline]
+  pub fn execute<
+    T: 'static,
+    V: 'static + NapiValue,
+    F: 'static + Future<Output = Result<T>>,
+    R: 'static + Send + Sync + FnOnce(&mut Env, T) -> Result<V>,
+  >(
+    &self,
+    deferred: F,
+    resolver: R,
+  ) -> Result<JsObject> {
+    use futures::prelude::*;
+
+    let mut raw_promise = ptr::null_mut();
+    let mut raw_deferred = ptr::null_mut();
+
+    unsafe {
+      let status = sys::napi_create_promise(self.0, &mut raw_deferred, &mut raw_promise);
+      check_status(status)?;
+    }
+
+    let event_loop = unsafe { sys::uv_default_loop() };
+    let raw_env = self.0;
+    let future_to_execute = promise::resolve_from_future(self.0, deferred, resolver, raw_deferred)
+      .map(move |v| match v {
+        Ok(value) => value,
+        Err(e) => {
+          let cloned_error = e.clone();
+          unsafe {
+            sys::napi_throw_error(raw_env, ptr::null(), e.reason.as_ptr() as *const _);
+          };
+          eprintln!("{:?}", &cloned_error);
+          panic!(cloned_error);
+        }
+      });
+    uv::execute(event_loop, Box::pin(future_to_execute))?;
+
+    Ok(JsObject::from_raw_unchecked(self.0, raw_promise))
+  }
+
+  #[inline]
   pub fn get_node_version(&self) -> Result<NodeVersion> {
     let mut result = ptr::null();
     check_status(unsafe { sys::napi_get_node_version(self.0, &mut result) })?;
@@ -426,13 +538,12 @@ impl Env {
 
 unsafe extern "C" fn drop_buffer(env: sys::napi_env, finalize_data: *mut c_void, len: *mut c_void) {
   let length = Box::from_raw(len as *mut u64);
-  let length = length.as_ref();
   let length = *length as usize;
   let _ = Vec::from_raw_parts(finalize_data as *mut u8, length, length);
   let mut changed = 0;
-  let ajust_external_memory_status =
+  let adjust_external_memory_status =
     sys::napi_adjust_external_memory(env, -(length as i64), &mut changed);
-  debug_assert!(Status::from(ajust_external_memory_status) == Status::Ok);
+  debug_assert!(Status::from(adjust_external_memory_status) == Status::Ok);
 }
 
 unsafe extern "C" fn raw_finalize<T>(
diff --git a/napi/src/js_values/mod.rs b/napi/src/js_values/mod.rs
index 84e4abad..3d3472d0 100644
--- a/napi/src/js_values/mod.rs
+++ b/napi/src/js_values/mod.rs
@@ -40,6 +40,7 @@ pub struct JsUndefined(pub(crate) Value);
 #[derive(Clone, Copy, Debug)]
 pub struct JsNull(pub(crate) Value);
 
+#[cfg(napi6)]
 #[derive(Clone, Copy, Debug)]
 pub struct JsBigint(pub(crate) Value);
 
@@ -165,6 +166,7 @@ impl_js_value_methods!(JsString);
 impl_js_value_methods!(JsObject);
 impl_js_value_methods!(JsFunction);
 impl_js_value_methods!(JsExternal);
+#[cfg(napi6)]
 impl_js_value_methods!(JsBigint);
 impl_js_value_methods!(JsSymbol);
 
@@ -178,6 +180,7 @@ impl_napi_value_trait!(JsString, String);
 impl_napi_value_trait!(JsObject, Object);
 impl_napi_value_trait!(JsFunction, Function);
 impl_napi_value_trait!(JsExternal, External);
+#[cfg(napi6)]
 impl_napi_value_trait!(JsBigint, Bigint);
 impl_napi_value_trait!(JsSymbol, Symbol);
 
diff --git a/napi/src/js_values/value_type.rs b/napi/src/js_values/value_type.rs
index 9163cd0e..2908e902 100644
--- a/napi/src/js_values/value_type.rs
+++ b/napi/src/js_values/value_type.rs
@@ -14,6 +14,7 @@ pub enum ValueType {
   Object = 6,
   Function = 7,
   External = 8,
+  #[cfg(napi6)]
   Bigint = 9,
 }
 
@@ -24,6 +25,7 @@ impl TryInto<sys::napi_valuetype> for ValueType {
     use sys::napi_valuetype::*;
     match self {
       ValueType::Unknown => Err(Error::from_status(Status::Unknown)),
+      #[cfg(napi6)]
       ValueType::Bigint => Ok(napi_bigint),
       ValueType::Boolean => Ok(napi_boolean),
       ValueType::External => Ok(napi_external),
@@ -42,6 +44,7 @@ impl From<sys::napi_valuetype> for ValueType {
   fn from(value: sys::napi_valuetype) -> Self {
     use sys::napi_valuetype::*;
     match value {
+      #[cfg(napi6)]
       napi_bigint => ValueType::Bigint,
       napi_boolean => ValueType::Boolean,
       napi_external => ValueType::External,
diff --git a/napi/src/lib.rs b/napi/src/lib.rs
index 879fffeb..33c296b0 100644
--- a/napi/src/lib.rs
+++ b/napi/src/lib.rs
@@ -4,10 +4,15 @@ mod env;
 mod error;
 mod js_values;
 mod module;
+#[cfg(all(feature = "libuv", napi4))]
+mod promise;
 mod status;
 pub mod sys;
 mod task;
+#[cfg(napi4)]
 pub mod threadsafe_function;
+#[cfg(all(feature = "libuv", napi4))]
+mod uv;
 mod version;
 
 pub use async_work::AsyncWork;
diff --git a/napi/src/promise.rs b/napi/src/promise.rs
new file mode 100644
index 00000000..0b13c319
--- /dev/null
+++ b/napi/src/promise.rs
@@ -0,0 +1,96 @@
+use futures::prelude::*;
+use std::os::raw::{c_char, c_void};
+use std::ptr;
+
+use crate::error::check_status;
+use crate::{sys, Env, NapiValue, Result};
+
+struct FuturePromise<T, V: NapiValue> {
+  deferred: sys::napi_deferred,
+  resolver: Box<dyn FnOnce(&mut Env, T) -> Result<V>>,
+}
+
+#[inline]
+pub async fn resolve_from_future<
+  T,
+  V: NapiValue,
+  R: FnOnce(&mut Env, T) -> Result<V> + 'static,
+  F: Future<Output = Result<T>>,
+>(
+  env: sys::napi_env,
+  fut: F,
+  resolver: R,
+  raw_deferred: sys::napi_deferred,
+) -> Result<()> {
+  let mut async_resource_name = ptr::null_mut();
+  let s = "napi_resolve_promise_from_future";
+  let status = unsafe {
+    sys::napi_create_string_utf8(
+      env,
+      s.as_ptr() as *const c_char,
+      s.len() as u64,
+      &mut async_resource_name,
+    )
+  };
+  check_status(status)?;
+
+  let initial_thread_count: u64 = 1;
+  let mut tsfn_value = ptr::null_mut();
+  let future_promise = FuturePromise {
+    deferred: raw_deferred,
+    resolver: Box::from(resolver),
+  };
+  let status = unsafe {
+    sys::napi_create_threadsafe_function(
+      env,
+      ptr::null_mut(),
+      ptr::null_mut(),
+      async_resource_name,
+      0,
+      initial_thread_count,
+      ptr::null_mut(),
+      None,
+      Box::leak(Box::from(future_promise)) as *mut _ as *mut c_void,
+      Some(call_js_cb::<T, V>),
+      &mut tsfn_value,
+    )
+  };
+  check_status(status)?;
+  let val = fut.await?;
+  check_status(unsafe {
+    sys::napi_call_threadsafe_function(
+      tsfn_value,
+      Box::into_raw(Box::from(val)) as *mut _ as *mut c_void,
+      sys::napi_threadsafe_function_call_mode::napi_tsfn_nonblocking,
+    )
+  })?;
+  check_status(unsafe {
+    sys::napi_release_threadsafe_function(
+      tsfn_value,
+      sys::napi_threadsafe_function_release_mode::napi_tsfn_release,
+    )
+  })
+}
+
+unsafe extern "C" fn call_js_cb<T, V: NapiValue>(
+  raw_env: sys::napi_env,
+  _js_callback: sys::napi_value,
+  context: *mut c_void,
+  data: *mut c_void,
+) {
+  let mut env = Env::from_raw(raw_env);
+  let future_promise = Box::from_raw(context as *mut FuturePromise<T, V>);
+  let value = ptr::read(data as *const _);
+  let js_value_to_resolve = (future_promise.resolver)(&mut env, value);
+  let deferred = future_promise.deferred;
+  match js_value_to_resolve {
+    Ok(v) => {
+      let status = sys::napi_resolve_deferred(raw_env, deferred, v.raw_value());
+      debug_assert!(status == sys::napi_status::napi_ok, "Resolve promise failed");
+    }
+    Err(e) => {
+      let status = sys::napi_reject_deferred(raw_env, deferred, e.into_raw(raw_env));
+      debug_assert!(status == sys::napi_status::napi_ok, "Reject promise failed");
+    }
+  };
+}
diff --git a/napi/src/status.rs b/napi/src/status.rs
index cb38de28..de981ed1 100644
--- a/napi/src/status.rs
+++ b/napi/src/status.rs
@@ -17,9 +17,11 @@ pub enum Status {
   EscapeCalledTwice,
   HandleScopeMismatch,
   CallbackScopeMismatch,
+  #[cfg(napi4)]
   QueueFull,
+  #[cfg(napi4)]
   Closing,
-  #[cfg(node6)]
+  #[cfg(napi6)]
   BigintExpected,
   Unknown,
 }
@@ -45,9 +47,11 @@ impl From<napi_status> for Status {
       napi_escape_called_twice => EscapeCalledTwice,
       napi_handle_scope_mismatch => HandleScopeMismatch,
       napi_callback_scope_mismatch => CallbackScopeMismatch,
+      #[cfg(napi4)]
       napi_queue_full => QueueFull,
+      #[cfg(napi4)]
       napi_closing => Closing,
-      #[cfg(node6)]
+      #[cfg(napi6)]
       napi_bigint_expected => BigintExpected,
       _ => Unknown,
     }
@@ -72,9 +76,11 @@ impl Into<self::napi_status> for Status {
       Self::EscapeCalledTwice => napi_status::napi_escape_called_twice,
       Self::HandleScopeMismatch => napi_status::napi_handle_scope_mismatch,
       Self::CallbackScopeMismatch => napi_status::napi_callback_scope_mismatch,
+      #[cfg(napi4)]
       Self::QueueFull => napi_status::napi_queue_full,
+      #[cfg(napi4)]
       Self::Closing => napi_status::napi_closing,
-      #[cfg(node6)]
+      #[cfg(napi6)]
       Self::BigintExpected => napi_status::napi_bigint_expected,
       Self::Unknown => napi_status::napi_generic_failure,
     }
diff --git a/napi/src/uv.rs b/napi/src/uv.rs
new file mode 100644
index 00000000..bf91fc19
--- /dev/null
+++ b/napi/src/uv.rs
@@ -0,0 +1,96 @@
+extern crate alloc;
+
+use alloc::alloc::{alloc, Layout};
+use futures::future::LocalBoxFuture;
+use futures::task::{waker, ArcWake, Context, Poll};
+use std::future::Future;
+use std::os::raw::c_void;
+use std::pin::Pin;
+use std::sync::Arc;
+
+use crate::{sys, Error, Result, Status};
+
+struct Task<'a> {
+  future: LocalBoxFuture<'a, ()>,
+  context: Context<'a>,
+}
+
+struct UvWaker(*mut sys::uv_async_t);
+
+unsafe impl Send for UvWaker {}
+unsafe impl Sync for UvWaker {}
+
+impl UvWaker {
+  fn new(event_loop: *mut sys::uv_loop_s) -> Result<UvWaker> {
+    let uv_async_t = unsafe { alloc(Layout::new::<sys::uv_async_t>()) as *mut sys::uv_async_t };
+    unsafe {
+      let status = sys::uv_async_init(event_loop, uv_async_t, Some(poll_future));
+      if status != 0 {
+        return Err(Error::new(
+          Status::Unknown,
+          "Non-zero status returned from uv_async_init".to_owned(),
+        ));
+      }
+    };
+    Ok(UvWaker(uv_async_t))
+  }
+
+  #[inline]
+  fn assign_task(&self, mut task: Task) {
+    if !task.poll_future() {
+      let arc_task = Arc::new(task);
+      unsafe {
+        sys::uv_handle_set_data(
+          self.0 as *mut sys::uv_handle_t,
+          Arc::into_raw(arc_task) as *mut c_void,
+        )
+      };
+    } else {
+      unsafe { sys::uv_close(self.0 as *mut sys::uv_handle_t, None) };
+    };
+  }
+}
+
+impl ArcWake for UvWaker {
+  fn wake_by_ref(arc_self: &Arc<Self>) {
+    let status = unsafe { sys::uv_async_send(arc_self.0) };
+    assert!(status == 0, "wake_uv_async_by_ref failed");
+  }
+}
+
+#[inline]
+pub fn execute(event_loop: *mut sys::uv_loop_s, future: LocalBoxFuture<()>) -> Result<()> {
+  let uv_waker = UvWaker::new(event_loop)?;
+  let arc_waker = Arc::new(uv_waker);
+  let waker_to_poll = Arc::clone(&arc_waker);
+  let waker = waker(arc_waker);
+  let context = Context::from_waker(&waker);
+  let task = Task { future, context };
+  waker_to_poll.assign_task(task);
+  Ok(())
+}
+
+impl<'a> Task<'a> {
+  fn poll_future(&mut self) -> bool {
+    let mut pinned = Pin::new(&mut self.future);
+    let fut_mut = pinned.as_mut();
+    match fut_mut.poll(&mut self.context) {
+      Poll::Ready(_) => true,
+      Poll::Pending => false,
+    }
+  }
+}
+
+unsafe extern "C" fn poll_future(handle: *mut sys::uv_async_t) {
+  let data_ptr = sys::uv_handle_get_data(handle as *mut sys::uv_handle_t) as *mut Task;
+  let mut task = Arc::from_raw(data_ptr);
+  if let Some(mut_task) = Arc::get_mut(&mut task) {
+    if mut_task.poll_future() {
+      sys::uv_close(handle as *mut sys::uv_handle_t, None);
+    } else {
+      Arc::into_raw(task);
+    };
+  } else {
+    Arc::into_raw(task);
+  }
+}
diff --git a/test_module/Cargo.toml b/test_module/Cargo.toml
index d0dfd8c1..4ed26aeb 100644
--- a/test_module/Cargo.toml
+++ b/test_module/Cargo.toml
@@ -8,7 +8,8 @@ edition = "2018"
 crate-type = ["cdylib"]
 
 [dependencies]
-napi-rs = { path = "../napi" }
+futures = "0.3"
+napi-rs = { path = "../napi", features = ["libuv"] }
 napi-rs-derive = { path = "../napi-derive" }
 tokio = { version = "0.2", features = ["default", "fs"]}
 
diff --git a/test_module/__test__/function.spec.js b/test_module/__test__/function.spec.js
index 103b8b7b..d23585cc 100644
--- a/test_module/__test__/function.spec.js
+++ b/test_module/__test__/function.spec.js
@@ -2,21 +2,15 @@ const test = require('ava')
 
 const bindings = require('../index.node')
 
-test('should call the function', async (t) => {
-  const ret = await new Promise((resolve) => {
-    bindings.testCallFunction((arg1, arg2) => {
-      resolve(`${arg1} ${arg2}`)
-    })
+test('should call the function', (t) => {
+  bindings.testCallFunction((arg1, arg2) => {
+    t.is(`${arg1} ${arg2}`, 'hello world')
   })
-  t.is(ret, 'hello world')
 })
 
-test('should set "this" properly', async (t) => {
+test('should set "this" properly', (t) => {
   const obj = {}
-  const ret = await new Promise((resolve) => {
-    bindings.testCallFunctionWithThis(obj, function () {
-      resolve(this)
-    })
+  bindings.testCallFunctionWithThis.call(obj, function () {
+    t.is(this, obj)
   })
-  t.is(ret, obj)
 })
diff --git a/test_module/__test__/get-napi-version.spec.js b/test_module/__test__/get-napi-version.spec.js
new file mode 100644
index 00000000..42a8eccc
--- /dev/null
+++ b/test_module/__test__/get-napi-version.spec.js
@@ -0,0 +1,9 @@
+const test = require('ava')
+
+const bindings = require('../index.node')
+
+test('should get napi version', (t) => {
+  const napiVersion = bindings.getNapiVersion()
+  t.true(typeof napiVersion === 'number')
+  t.is(`${napiVersion}`, process.versions.napi)
+})
diff --git a/test_module/__test__/example.txt b/test_module/__test__/napi4/example.txt
similarity index 100%
rename from test_module/__test__/example.txt
rename to test_module/__test__/napi4/example.txt
diff --git a/test_module/__test__/threadsafe_function.spec.js b/test_module/__test__/napi4/threadsafe_function.spec.js
similarity index 68%
rename from test_module/__test__/threadsafe_function.spec.js
rename to test_module/__test__/napi4/threadsafe_function.spec.js
index eac5de27..418db223 100644
--- a/test_module/__test__/threadsafe_function.spec.js
+++ b/test_module/__test__/napi4/threadsafe_function.spec.js
@@ -1,9 +1,16 @@
 const test = require('ava')
-const bindings = require('../index.node')
+
+const bindings = require('../../index.node')
+const napiVersion = require('../napi-version')
 
 test('should get js function called from a thread', async (t) => {
   let called = 0
 
+  if (napiVersion < 4) {
+    t.is(bindings.testThreadsafeFunction, undefined)
+    return
+  }
+
   return new Promise((resolve, reject) => {
     bindings.testThreadsafeFunction((...args) => {
       called += 1
diff --git a/test_module/__test__/tokio_readfile.spec.js b/test_module/__test__/napi4/tokio_readfile.spec.js
similarity index 74%
rename from test_module/__test__/tokio_readfile.spec.js
rename to test_module/__test__/napi4/tokio_readfile.spec.js
index 695caa03..6c39c027 100644
--- a/test_module/__test__/tokio_readfile.spec.js
+++ b/test_module/__test__/napi4/tokio_readfile.spec.js
@@ -1,11 +1,17 @@
 const test = require('ava')
 const fs = require('fs')
 const path = require('path')
-const bindings = require('../index.node')
+
+const bindings = require('../../index.node')
+const napiVersion = require('../napi-version')
 
 const filepath = path.resolve(__dirname, './example.txt')
 
 test('should read a file and return its a buffer', async (t) => {
+  if (napiVersion < 4) {
+    t.is(bindings.testTokioReadfile, undefined)
+    return
+  }
   return new Promise((resolve, reject) => {
     bindings.testTokioReadfile(filepath, (err, value) => {
       try {
diff --git a/test_module/__test__/tsfn_error.spec.js b/test_module/__test__/napi4/tsfn_error.spec.js
similarity index 67%
rename from test_module/__test__/tsfn_error.spec.js
rename to test_module/__test__/napi4/tsfn_error.spec.js
index d692a920..ad5a5468 100644
--- a/test_module/__test__/tsfn_error.spec.js
+++ b/test_module/__test__/napi4/tsfn_error.spec.js
@@ -1,7 +1,13 @@
 const test = require('ava')
-const bindings = require('../index.node')
+
+const bindings = require('../../index.node')
+const napiVersion = require('../napi-version')
 
 test('should call callback with the first arguments as an Error', async (t) => {
+  if (napiVersion < 4) {
+    t.is(bindings.testTsfnError, undefined)
+    return
+  }
   return new Promise((resolve, reject) => {
     bindings.testTsfnError((err) => {
       try {
diff --git a/test_module/__test__/napi4/uv.spec.js b/test_module/__test__/napi4/uv.spec.js
new file mode 100644
index 00000000..d31eeaae
--- /dev/null
+++ b/test_module/__test__/napi4/uv.spec.js
@@ -0,0 +1,18 @@
+const test = require('ava')
+const { join } = require('path')
+const { readFileSync } = require('fs')
+
+const bindings = require('../../index.node')
+const napiVersion = require('../napi-version')
+
+const filepath = join(__dirname, './example.txt')
+
+test('should call callback with the first arguments as an Error', async (t) => {
+  if (napiVersion < 4) {
+    t.is(bindings.uvReadFile, undefined)
+    return
+  }
+  const fileContent = await bindings.uvReadFile(filepath)
+  t.true(Buffer.isBuffer(fileContent))
+  t.deepEqual(readFileSync(filepath), fileContent)
+})
diff --git a/test_module/src/function.rs b/test_module/src/function.rs
index 6e7a13ec..733f7f8e 100644
--- a/test_module/src/function.rs
+++ b/test_module/src/function.rs
@@ -8,15 +8,15 @@ pub fn call_function(ctx: CallContext) -> Result<JsNull> {
 
   js_func.call(None, &[js_string_hello, js_string_world])?;
 
-  Ok(ctx.env.get_null()?)
+  ctx.env.get_null()
 }
 
-#[js_function(2)]
-pub fn call_function_with_this(ctx: CallContext) -> Result<JsNull> {
-  let js_this = ctx.get::<JsObject>(0)?;
-  let js_func = ctx.get::<JsFunction>(1)?;
+#[js_function(1)]
+pub fn call_function_with_this(ctx: CallContext<JsObject>) -> Result<JsNull> {
+  let js_this = ctx.this;
+  let js_func = ctx.get::<JsFunction>(0)?;
 
   js_func.call(Some(&js_this), &[])?;
 
-  Ok(ctx.env.get_null()?)
+  ctx.env.get_null()
 }
diff --git a/test_module/src/lib.rs b/test_module/src/lib.rs
index bcf0847c..b01a595a 100644
--- a/test_module/src/lib.rs
+++ b/test_module/src/lib.rs
@@ -5,6 +5,10 @@ extern crate napi_rs_derive;
 
 use napi::{CallContext, Error, JsString, JsUnknown, Module, Result, Status};
 
+#[cfg(napi4)]
+mod napi4;
+#[cfg(napi4)]
+mod libuv;
 #[cfg(napi5)]
 mod napi5;
 
@@ -13,16 +17,20 @@ mod function;
 mod external;
 mod symbol;
 mod task;
-mod tsfn;
+mod napi_version;
 
 use buffer::{buffer_to_string, get_buffer_length};
 use function::{call_function, call_function_with_this};
 use external::{create_external, get_external_count};
+#[cfg(napi4)]
+use napi4::{test_threadsafe_function, test_tokio_readfile, test_tsfn_error};
 #[cfg(napi5)]
 use napi5::is_date::test_object_is_date;
 use symbol::{create_named_symbol, create_symbol_from_js_string, create_unnamed_symbol};
 use task::test_spawn_thread;
-use tsfn::{test_threadsafe_function, test_tokio_readfile, test_tsfn_error};
+#[cfg(napi4)]
+use libuv::read_file::uv_read_file;
+use napi_version::get_napi_version;
 
 register_module!(test_module, init);
 
@@ -37,11 +45,17 @@ fn init(module: &mut Module) -> Result<()> {
   module.create_named_method("createNamedSymbol", create_named_symbol)?;
   module.create_named_method("createUnnamedSymbol", create_unnamed_symbol)?;
   module.create_named_method("createSymbolFromJsString", create_symbol_from_js_string)?;
-  module.create_named_method("testTsfnError", test_tsfn_error)?;
-  module.create_named_method("testThreadsafeFunction", test_threadsafe_function)?;
-  module.create_named_method("testTokioReadfile", test_tokio_readfile)?;
+  module.create_named_method("getNapiVersion", get_napi_version)?;
   module.create_named_method("testCallFunction", call_function)?;
   module.create_named_method("testCallFunctionWithThis", call_function_with_this)?;
+  #[cfg(napi4)]
+  module.create_named_method("testTsfnError", test_tsfn_error)?;
+  #[cfg(napi4)]
+  module.create_named_method("testThreadsafeFunction", test_threadsafe_function)?;
+  #[cfg(napi4)]
+  module.create_named_method("testTokioReadfile", test_tokio_readfile)?;
+  #[cfg(napi4)]
+  module.create_named_method("uvReadFile", uv_read_file)?;
   #[cfg(napi5)]
   module.create_named_method("testObjectIsDate", test_object_is_date)?;
   Ok(())
diff --git a/test_module/src/libuv/mod.rs b/test_module/src/libuv/mod.rs
new file mode 100644
index 00000000..1cbe4ba6
--- /dev/null
+++ b/test_module/src/libuv/mod.rs
@@ -0,0 +1 @@
+pub mod read_file;
diff --git a/test_module/src/libuv/read_file.rs b/test_module/src/libuv/read_file.rs
new file mode 100644
index 00000000..04258f56
--- /dev/null
+++ b/test_module/src/libuv/read_file.rs
@@ -0,0 +1,20 @@
+use std::thread;
+use std::fs;
+
+use futures::prelude::*;
+use futures::channel::oneshot;
+use napi::{CallContext, Result, JsString, JsObject, Status, Error};
+
+#[js_function(1)]
+pub fn uv_read_file(ctx: CallContext) -> Result<JsObject> {
+  let path = ctx.get::<JsString>(0)?;
+  let (sender, receiver) = oneshot::channel();
+  let p = path.as_str()?.to_owned();
+  thread::spawn(|| {
+    let res = fs::read(p).map_err(|e| Error::new(Status::Unknown, format!("{}", e)));
+    sender.send(res).expect("Send data failed");
+  });
+  ctx.env.execute(receiver.map_err(|e| Error::new(Status::Unknown, format!("{}", e))).map(|x| x.and_then(|x| x)), |&mut env, data| {
+    env.create_buffer_with_data(data)
+  })
+}
diff --git a/test_module/src/napi4/mod.rs b/test_module/src/napi4/mod.rs
new file mode 100644
index 00000000..832dd8ee
--- /dev/null
+++ b/test_module/src/napi4/mod.rs
@@ -0,0 +1,3 @@
+mod tsfn;
+
+pub use tsfn::*;
diff --git a/test_module/src/tsfn.rs b/test_module/src/napi4/tsfn.rs
similarity index 100%
rename from test_module/src/tsfn.rs
rename to test_module/src/napi4/tsfn.rs
diff --git a/test_module/src/napi_version.rs b/test_module/src/napi_version.rs
new file mode 100644
index 00000000..158385b0
--- /dev/null
+++ b/test_module/src/napi_version.rs
@@ -0,0 +1,6 @@
+use napi::{CallContext, JsNumber, Result};
+
+#[js_function]
+pub fn get_napi_version(ctx: CallContext) -> Result<JsNumber> {
+  ctx.env.create_uint32(ctx.env.get_napi_version()?)
+}
diff --git a/test_module/yarn.lock b/test_module/yarn.lock
deleted file mode 100644
index fb57ccd1..00000000
--- a/test_module/yarn.lock
+++ /dev/null
@@ -1,4 +0,0 @@
-# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
-# yarn lockfile v1
-
-