diff --git a/.github/workflows/linux.yaml b/.github/workflows/linux.yaml
index d4042c75..65639baf 100644
--- a/.github/workflows/linux.yaml
+++ b/.github/workflows/linux.yaml
@@ -50,25 +50,27 @@ jobs:
           path: target
           key: ${{ matrix.version }}-x86_64-unknown-linux-gnu-cargo-build-trimmed-${{ hashFiles('**/Cargo.lock') }}
 
-      - name: check build
+      - name: Check build
         uses: actions-rs/cargo@v1
         with:
           command: check
           args: --all --bins --examples --tests -vvv
 
-      - name: tests
+      - name: Tests
         uses: actions-rs/cargo@v1
-        timeout-minutes: 40
+        timeout-minutes: 5
         with:
           command: test
           args: -p napi-rs --lib -- --nocapture
 
-      - name: test scripts
+      - name: Fuzzy tests
         run: |
           yarn
           cd test_module
           yarn build
-          yarn test
+          node fuzzy.js
+        env:
+          RUST_BACKTRACE: 1
 
       - name: Clear the cargo caches
         run: |
diff --git a/.github/workflows/macos.yaml b/.github/workflows/macos.yaml
index b0765a34..c6bdb536 100644
--- a/.github/workflows/macos.yaml
+++ b/.github/workflows/macos.yaml
@@ -50,25 +50,27 @@ jobs:
           path: target
           key: ${{ matrix.version }}-x86_64-apple-darwin-cargo-build-trimmed-${{ hashFiles('**/Cargo.lock') }}
 
-      - name: check build
+      - name: Check build
         uses: actions-rs/cargo@v1
         with:
           command: check
           args: --all --bins --examples --tests -vvv
 
-      - name: tests
+      - name: Tests
         uses: actions-rs/cargo@v1
-        timeout-minutes: 40
+        timeout-minutes: 5
         with:
           command: test
           args: -p napi-rs --lib -- --nocapture
 
-      - name: test scripts
+      - name: Fuzzy tests
         run: |
           yarn
           cd test_module
           yarn build
-          yarn test
+          node fuzzy.js
+        env:
+          RUST_BACKTRACE: 1
 
       - name: Clear the cargo caches
         run: |
diff --git a/.github/workflows/windows.yaml b/.github/workflows/windows.yaml
index b46b26ef..e75f6686 100644
--- a/.github/workflows/windows.yaml
+++ b/.github/workflows/windows.yaml
@@ -56,25 +56,25 @@ jobs:
           path: target
           key: ${{ matrix.version }}-${{ matrix.target }}-cargo-build-trimmed-${{ hashFiles('**/Cargo.lock') }}
 
-      - name: check build
+      - name: Check build
         uses: actions-rs/cargo@v1
         with:
           command: check
           args: -p napi-rs -vvv
 
-      - name: tests
+      - name: Tests
         uses: actions-rs/cargo@v1
-        timeout-minutes: 40
+        timeout-minutes: 5
         with:
           command: test
           args: -p napi-rs --lib -- --nocapture
 
-      - name: test scripts
+      - name: Fuzzy tests
         run: |
           yarn
           cd test_module
           yarn build
-          yarn test
+          node fuzzy.js
         env:
           RUST_BACKTRACE: 1
 
diff --git a/napi/Cargo.toml b/napi/Cargo.toml
index 5fe0f188..b2c56310 100644
--- a/napi/Cargo.toml
+++ b/napi/Cargo.toml
@@ -11,9 +11,6 @@ edition = "2018"
 
 [dependencies]
 futures = { version = "0.3", features = ["default", "thread-pool"] }
-num_cpus = "1.13"
-once_cell = "1.3"
-threadpool = "1.8"
 
 [target.'cfg(windows)'.build-dependencies]
 flate2 = "1.0"
diff --git a/napi/src/async_work.rs b/napi/src/async_work.rs
new file mode 100644
index 00000000..e6f57b3c
--- /dev/null
+++ b/napi/src/async_work.rs
@@ -0,0 +1,114 @@
+use std::mem;
+use std::os::raw::{c_char, c_void};
+use std::ptr;
+
+use crate::{check_status, sys, Env, Result, Task};
+
+pub struct AsyncWork<T: Task> {
+  inner_task: T,
+  deferred: sys::napi_deferred,
+  value: Result<*mut T::Output>,
+}
+
+impl<T: Task> AsyncWork<T> {
+  pub fn run(env: sys::napi_env, task: T, deferred: sys::napi_deferred) -> Result<()> {
+    let mut raw_resource = ptr::null_mut();
+    let status = unsafe { sys::napi_create_object(env, &mut raw_resource) };
+    check_status(status)?;
+    let mut raw_name = ptr::null_mut();
+    let s = "napi_rs_async";
+    let status = unsafe {
+      sys::napi_create_string_utf8(
+        env,
+        s.as_ptr() as *const c_char,
+        s.len() as u64,
+        &mut raw_name,
+      )
+    };
+    check_status(status)?;
+    let mut raw_context = ptr::null_mut();
+    unsafe {
+      let status = sys::napi_async_init(env, raw_resource, raw_name, &mut raw_context);
+      check_status(status)?;
+    };
+    let result = AsyncWork {
+      inner_task: task,
+      deferred,
+      value: Ok(ptr::null_mut()),
+    };
+    let mut async_work = ptr::null_mut();
+    check_status(unsafe {
+      sys::napi_create_async_work(
+        env,
+        raw_resource,
+        raw_name,
+        Some(execute::<T> as unsafe extern "C" fn(env: sys::napi_env, data: *mut c_void)),
+        Some(
+          complete::<T>
+            as unsafe extern "C" fn(
+              env: sys::napi_env,
+              status: sys::napi_status,
+              data: *mut c_void,
+            ),
+        ),
+        Box::leak(Box::new(result)) as *mut _ as *mut c_void,
+        &mut async_work,
+      )
+    })?;
+    check_status(unsafe { sys::napi_queue_async_work(env, async_work) })
+  }
+}
+
+unsafe impl<T: Task> Send for AsyncWork<T> {}
+
+unsafe impl<T: Task> Sync for AsyncWork<T> {}
+
+unsafe extern "C" fn execute<T: Task>(_env: sys::napi_env, data: *mut c_void) {
+  let mut work = Box::from_raw(data as *mut AsyncWork<T>);
+  work.value = work
+    .inner_task
+    .compute()
+    .map(|v| Box::into_raw(Box::from(v)));
+  Box::leak(work);
+}
+
+unsafe extern "C" fn complete<T: Task>(
+  env: sys::napi_env,
+  status: sys::napi_status,
+  data: *mut c_void,
+) {
+  let mut work = Box::from_raw(data as *mut AsyncWork<T>);
+  let value_ptr = mem::replace(&mut work.value, Ok(ptr::null_mut()));
+  let deferred = mem::replace(&mut work.deferred, ptr::null_mut());
+  let value = value_ptr.and_then(move |v| {
+    let mut env = Env::from_raw(env);
+    let output = ptr::read(v as *const _);
+    work.inner_task.resolve(&mut env, output)
+  });
+  let mut handle_scope = ptr::null_mut();
+  match check_status(status).and_then(move |_| value) {
+    Ok(v) => {
+      let open_handle_status = sys::napi_open_handle_scope(env, &mut handle_scope);
+      debug_assert!(
+        open_handle_status == sys::napi_status::napi_ok,
+        "OpenHandleScope failed"
+      );
+      let status = sys::napi_resolve_deferred(env, deferred, v.raw_value);
+      debug_assert!(status == sys::napi_status::napi_ok, "Reject promise failed");
+    }
+    Err(e) => {
+      let open_handle_status = sys::napi_open_handle_scope(env, &mut handle_scope);
+      debug_assert!(
+        open_handle_status == sys::napi_status::napi_ok,
+        "OpenHandleScope failed"
+      );
+      let status = sys::napi_reject_deferred(env, deferred, e.into_raw(env));
+      debug_assert!(status == sys::napi_status::napi_ok, "Reject promise failed");
+    }
+  };
+  let close_handle_scope_status = sys::napi_close_handle_scope(env, handle_scope);
+  debug_assert!(
+    close_handle_scope_status == sys::napi_status::napi_ok,
+    "Close handle scope failed"
+  );
+}
diff --git a/napi/src/executor.rs b/napi/src/executor.rs
index ef3da6f6..b2ce3064 100644
--- a/napi/src/executor.rs
+++ b/napi/src/executor.rs
@@ -1,82 +1,99 @@
-use futures::task::Poll;
-use std::alloc::{alloc, Layout};
+extern crate alloc;
+
+use alloc::alloc::{alloc, alloc_zeroed, 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::atomic::{AtomicBool, Ordering};
 use std::sync::Arc;
-use std::task::{Context, RawWaker, RawWakerVTable, Waker};
 
 use crate::{sys, Error, Result, Status};
 
-const UV_ASYNC_V_TABLE: RawWakerVTable = RawWakerVTable::new(
-  clone_executor,
-  wake_uv_async,
-  wake_uv_async_by_ref,
-  drop_uv_async,
-);
-
-unsafe fn clone_executor(uv_async_t: *const ()) -> RawWaker {
-  RawWaker::new(uv_async_t, &UV_ASYNC_V_TABLE)
-}
-
-unsafe fn wake_uv_async(uv_async_t: *const ()) {
-  let status = sys::uv_async_send(uv_async_t as *mut sys::uv_async_t);
-  assert!(status == 0, "wake_uv_async failed");
-}
-
-unsafe fn wake_uv_async_by_ref(uv_async_t: *const ()) {
-  let status = sys::uv_async_send(uv_async_t as *mut sys::uv_async_t);
-  assert!(status == 0, "wake_uv_async_by_ref failed");
-}
-
-unsafe fn drop_uv_async(_uv_async_t_ptr: *const ()) {}
-
 struct Task<'a> {
-  future: Pin<Box<dyn Future<Output = ()>>>,
+  future: LocalBoxFuture<'a, ()>,
   context: Context<'a>,
+  is_polling: AtomicBool,
+}
+
+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 {
+      let layout = Layout::new::<sys::uv_async_t>();
+      debug_assert!(layout.size() != 0, "uv_async_t alloc size should not be 0");
+      if cfg!(windows) {
+        alloc_zeroed(layout) as *mut sys::uv_async_t
+      } else {
+        alloc(layout) 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 {
+          status: Status::Unknown,
+          reason: Some("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() {
+      task.is_polling.store(false, Ordering::Relaxed);
+      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<F: 'static + Future<Output = ()>>(
-  event_loop: *mut sys::uv_loop_s,
-  future: F,
-) -> Result<()> {
-  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 {
-        status: Status::Unknown,
-        reason: Some("Non-zero status returned from uv_async_init".to_owned()),
-      });
-    }
+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,
+    is_polling: AtomicBool::from(false),
   };
-  unsafe {
-    let waker = Waker::from_raw(RawWaker::new(
-      uv_async_t as *const _ as *const (),
-      &UV_ASYNC_V_TABLE,
-    ));
-    let context = Context::from_waker(&waker);
-    let mut task = Task {
-      future: Box::pin(future),
-      context,
-    };
-    if !task.poll_future() {
-      let arc_task = Arc::new(task);
-      sys::uv_handle_set_data(
-        uv_async_t as *mut _ as *mut sys::uv_handle_t,
-        Arc::into_raw(arc_task) as *mut c_void,
-      );
-    } else {
-      sys::uv_close(uv_async_t as *mut _ as *mut sys::uv_handle_t, None);
-    };
-    Ok(())
-  }
+  waker_to_poll.assign_task(task);
+  Ok(())
 }
 
 impl<'a> Task<'a> {
   fn poll_future(&mut self) -> bool {
-    match self.future.as_mut().poll(&mut self.context) {
+    if self.is_polling.load(Ordering::Relaxed) {
+      return false;
+    }
+    self.is_polling.store(true, Ordering::Relaxed);
+    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,
     }
@@ -90,6 +107,7 @@ unsafe extern "C" fn poll_future(handle: *mut sys::uv_async_t) {
     if mut_task.poll_future() {
       sys::uv_close(handle as *mut sys::uv_handle_t, None);
     } else {
+      mut_task.is_polling.store(false, Ordering::Relaxed);
       Arc::into_raw(task);
     };
   } else {
diff --git a/napi/src/lib.rs b/napi/src/lib.rs
index 6964fbff..67bc73f8 100644
--- a/napi/src/lib.rs
+++ b/napi/src/lib.rs
@@ -1,8 +1,6 @@
+use async_work::AsyncWork;
 use core::fmt::Debug;
-use futures::channel::oneshot::channel;
 use futures::prelude::*;
-use num_cpus::get_physical;
-use once_cell::sync::OnceCell;
 use std::any::TypeId;
 use std::convert::{TryFrom, TryInto};
 use std::ffi::CString;
@@ -14,9 +12,8 @@ use std::ptr;
 use std::slice;
 use std::str;
 use std::string::String as RustString;
-use std::sync::Arc;
-use threadpool::ThreadPool;
 
+mod async_work;
 mod call_context;
 mod executor;
 mod promise;
@@ -27,14 +24,11 @@ mod version;
 pub use call_context::CallContext;
 pub use sys::{napi_valuetype, Status};
 pub use task::Task;
-use task::{NapiRSThreadPool, ThreadSafeTask};
 pub use version::NodeVersion;
 
 pub type Result<T> = std::result::Result<T, Error>;
 pub type Callback = extern "C" fn(sys::napi_env, sys::napi_callback_info) -> sys::napi_value;
 
-static THREAD_POOL: OnceCell<NapiRSThreadPool> = OnceCell::new();
-
 #[derive(Debug, Clone)]
 pub struct Error {
   pub status: Status,
@@ -179,6 +173,27 @@ impl Error {
       reason: None,
     }
   }
+
+  pub fn into_raw(self, env: sys::napi_env) -> sys::napi_value {
+    let mut err = ptr::null_mut();
+    let s = self.reason.unwrap_or("NAPI error".to_owned());
+    unsafe {
+      let mut err_reason = ptr::null_mut();
+      let status = sys::napi_create_string_utf8(
+        env,
+        s.as_ptr() as *const c_char,
+        s.len() as u64,
+        &mut err_reason,
+      );
+      debug_assert!(
+        status == sys::napi_status::napi_ok,
+        "Create error reason failed"
+      );
+      let status = sys::napi_create_error(env, ptr::null_mut(), err_reason, &mut err);
+      debug_assert!(status == sys::napi_status::napi_ok, "Create error failed");
+    };
+    err
+  }
 }
 
 impl From<std::ffi::NulError> for Error {
@@ -555,8 +570,7 @@ impl Env {
 
     let event_loop = unsafe { sys::uv_default_loop() };
     let raw_env = self.0;
-    executor::execute(
-      event_loop,
+    let future_to_execute =
       promise::resolve(self.0, deferred, resolver, raw_deferred).map(move |v| match v {
         Ok(value) => value,
         Err(e) => {
@@ -571,47 +585,19 @@ impl Env {
           eprintln!("{:?}", &cloned_error);
           panic!(cloned_error);
         }
-      }),
-    )?;
+      });
+    executor::execute(event_loop, Box::pin(future_to_execute))?;
 
     Ok(Value::from_raw_value(self, raw_promise, Object))
   }
 
-  #[inline]
-  pub fn spawn<
-    V: 'static + ValueType,
-    O: Send + 'static,
-    T: 'static + Send + Task<Output = O, JsValue = V>,
-  >(
-    &self,
-    task: T,
-  ) -> Result<Value<Object>> {
-    let (sender, receiver) = channel::<Result<O>>();
-    let threadpool =
-      THREAD_POOL.get_or_init(|| NapiRSThreadPool(ThreadPool::new(get_physical() * 2)));
-    let inner_task = Arc::new(ThreadSafeTask::new(task));
-    let thread_task = Arc::clone(&inner_task);
-    let promise_task = Arc::clone(&inner_task);
-    threadpool.0.execute(move || {
-      let value = thread_task.borrow().compute();
-      match sender.send(value) {
-        Err(e) => panic!(e),
-        _ => {}
-      };
-    });
-    let rev_value = async {
-      let result = receiver.await;
-      result
-        .map_err(|_| Error {
-          status: Status::Cancelled,
-          reason: Some("Receiver cancelled".to_owned()),
-        })
-        .and_then(|v| v)
-    };
+  pub fn spawn<T: 'static + Task>(&self, task: T) -> Result<Value<Object>> {
+    let mut raw_promise = ptr::null_mut();
+    let mut raw_deferred = ptr::null_mut();
 
-    self.execute(rev_value, move |env, v| {
-      promise_task.borrow().resolve(env, v)
-    })
+    check_status(unsafe { sys::napi_create_promise(self.0, &mut raw_deferred, &mut raw_promise) })?;
+    AsyncWork::run(self.0, task, raw_deferred)?;
+    Ok(Value::from_raw_value(self, raw_promise, Object))
   }
 
   pub fn get_node_version(&self) -> Result<NodeVersion> {
diff --git a/napi/src/task.rs b/napi/src/task.rs
index 0b636de5..3951a403 100644
--- a/napi/src/task.rs
+++ b/napi/src/task.rs
@@ -1,40 +1,10 @@
-use threadpool::ThreadPool;
-
 use crate::{Env, Result, Value, ValueType};
 
-pub struct NapiRSThreadPool(pub ThreadPool);
-
-unsafe impl Send for NapiRSThreadPool {}
-
-unsafe impl Sync for NapiRSThreadPool {}
-
 pub trait Task {
-  type Output: Send + 'static;
+  type Output: Send + Sized + 'static;
   type JsValue: ValueType;
 
-  fn compute(&mut self) -> Result<Self::Output>;
+  fn compute(&self) -> Result<Self::Output>;
 
   fn resolve(&self, env: &mut Env, output: Self::Output) -> Result<Value<Self::JsValue>>;
 }
-
-pub struct ThreadSafeTask<T: Task>(pub *mut T);
-
-impl<T: Task> ThreadSafeTask<T> {
-  pub fn new(task: T) -> ThreadSafeTask<T> {
-    ThreadSafeTask(Box::into_raw(Box::new(task)))
-  }
-
-  #[inline]
-  pub fn borrow(&self) -> &'static mut T {
-    Box::leak(unsafe { Box::from_raw(self.0) })
-  }
-}
-
-impl<T: Task> Drop for ThreadSafeTask<T> {
-  fn drop(&mut self) {
-    unsafe { Box::from_raw(self.0) };
-  }
-}
-
-unsafe impl<T: Task> Send for ThreadSafeTask<T> {}
-unsafe impl<T: Task> Sync for ThreadSafeTask<T> {}
diff --git a/package.json b/package.json
index 8dafa3d9..174e66c9 100644
--- a/package.json
+++ b/package.json
@@ -18,9 +18,10 @@
   ],
   "license": "MIT",
   "scripts": {
-    "format": "run-p format:md format:json format:yaml format:source",
+    "format": "run-p format:md format:json format:yaml format:source format:rs",
     "format:md": "prettier --parser markdown --write './**/*.md'",
     "format:json": "prettier --parser json --write './**/*.json'",
+    "format:rs": "cargo fmt",
     "format:source": "prettier --config ./package.json --write './**/*.js'",
     "format:yaml": "prettier --parser yaml --write './**/*.{yml,yaml}'"
   },
diff --git a/test_module/index.js b/test_module/future.js
similarity index 54%
rename from test_module/index.js
rename to test_module/future.js
index aa8a95cf..f96b98c7 100644
--- a/test_module/index.js
+++ b/test_module/future.js
@@ -9,30 +9,17 @@ function testThrow() {
   console.log('=== Test throwing from Rust')
   try {
     testModule.testThrow()
-    console.error('Expected function to throw an error')
+    console.log('Expected function to throw an error')
     process.exit(1)
   } catch (e) {
-    console.error(e)
+    console.log(e)
   }
 }
-
-function testSpawnThread(n) {
-  console.info('=== Test spawn task to threadpool')
-  return testModule.testSpawnThread(n)
-}
-
-const future = testSpawn()
-
-future
+testSpawn()
   .then((value) => {
     console.info(`${value} from napi`)
     testThrow()
   })
-  .then(() => testSpawnThread(20))
-  .then((value) => {
-    console.assert(value === 6765)
-    console.info('=== fibonacci result', value)
-  })
   .catch((e) => {
     console.error(e)
     process.exit(1)
diff --git a/test_module/fuzzy.js b/test_module/fuzzy.js
new file mode 100644
index 00000000..7a676778
--- /dev/null
+++ b/test_module/fuzzy.js
@@ -0,0 +1,34 @@
+const { exec } = require('child_process')
+
+Array.from({ length: 500 })
+  .reduce(async (acc) => {
+    await acc
+    await run()
+  }, null)
+  .then(() => {
+    console.info(`Fuzzy test success, passed ${500} tests.`)
+  })
+  .catch((e) => {
+    console.error(e)
+    process.exit(1)
+  })
+
+const run = () => {
+  return new Promise((resolve, reject) => {
+    const testProcess = exec('node ./spawn.js', {
+      env: process.env,
+    })
+    testProcess.stdout.pipe(process.stdout)
+    testProcess.stderr.pipe(process.stderr)
+    testProcess.on('error', (err) => {
+      reject(err)
+    })
+    testProcess.on('exit', (code) => {
+      if (code) {
+        reject(new TypeError(`Child process exit code ${code}`))
+      } else {
+        resolve()
+      }
+    })
+  })
+}
diff --git a/test_module/spawn.js b/test_module/spawn.js
new file mode 100644
index 00000000..56a6417f
--- /dev/null
+++ b/test_module/spawn.js
@@ -0,0 +1,16 @@
+const testModule = require('./index.node')
+
+function testSpawnThread(n) {
+  console.info('=== Test spawn task to threadpool')
+  return testModule.testSpawnThread(n)
+}
+
+testSpawnThread(20)
+  .then((value) => {
+    console.assert(value === 6765)
+    console.info('=== fibonacci result', value)
+  })
+  .catch((e) => {
+    console.error(e)
+    process.exit(1)
+  })
diff --git a/test_module/src/lib.rs b/test_module/src/lib.rs
index 9d0f249b..de7adc3a 100644
--- a/test_module/src/lib.rs
+++ b/test_module/src/lib.rs
@@ -57,7 +57,7 @@ impl Task for ComputeFib {
   type Output = u32;
   type JsValue = Number;
 
-  fn compute(&mut self) -> Result<Self::Output> {
+  fn compute(&self) -> Result<Self::Output> {
     Ok(fibonacci_native(self.n))
   }