napi-rs/examples/napi/src/async.rs

use futures::prelude::*;
use napi::bindgen_prelude::*;
use tokio::fs;

#[napi]
async fn read_file_async(path: String) -> Result<Buffer> {
  fs::read(path)
    .map(|r| match r {
      Ok(content) => Ok(content.into()),
      Err(e) => Err(Error::new(
        Status::GenericFailure,
        format!("failed to read file, {}", e),
      )),
    })
    .await
}