message: refactor(client): replace futures mpsc for tokio mpsc in dispatcher
diff: -use futures_channel::{mpsc, oneshot};
  -use futures_core::Stream;
  +use futures_channel::oneshot;
  use futures_util::future;
  +use tokio::sync::mpsc;
  use crate::common::{task, Future, Pin, Poll};
  @@ -8,7 +8,7 @@ pub type RetryPromise<T, U> = oneshot::Receiver<Result<U, (crate::Error, Option<
  pub type Promise<T> = oneshot::Receiver<Result<T, crate::Error>>;
  pub fn channel<T, U>() -> (Sender<T, U>, Receiver<T, U>) {
  - let (tx, rx) = mpsc::unbounded();
  + let (tx, rx) = mpsc::unbounded_channel();
  let (giver, taker) = want::new();
  let tx = Sender {
  buffered_once: false,
  @@ -81,9 +81,9 @@ impl<T, U> Sender<T, U> {
  }
  let (tx, rx) = oneshot::channel();
  self.inner
  - .unbounded_send(Envelope(Some((val, Callback::Retry(tx)))))
  + .send(Envelope(Some((val, Callback::Retry(tx)))))
  .map(move |_| rx)
  - .map_err(|e| e.into_inner().0.take().expect("envelope not dropped").0)
  + .map_err(|mut e| (e.0).0.take().expect("envelope not dropped").0)
  }
  pub fn send(&mut self, val: T) -> Result<Promise<U>, T> {
  @@ -92,9 +92,9 @@ impl<T, U> Sender<T, U> {
  }
  let (tx, rx) = oneshot::channel();
  self.inner
  - .unbounded_send(Envelope(Some((val, Callback::NoRetry(tx)))))
  + .send(Envelope(Some((val, Callback::NoRetry(tx)))))
  .map(move |_| rx)
  - .map_err(|e| e.into_inner().0.take().expect("envelope not dropped").0)
  + .map_err(|mut e| (e.0).0.take().expect("envelope not dropped").0)
  }
  pub fn unbound(self) -> UnboundedSender<T, U> {
  @@ -117,9 +117,9 @@ impl<T, U> UnboundedSender<T, U> {
  pub fn try_send(&mut self, val: T) -> Result<RetryPromise<T, U>, T> {
  let (tx, rx) = oneshot::channel();
  self.inner
  - .unbounded_send(Envelope(Some((val, Callback::Retry(tx)))))
  + .send(Envelope(Some((val, Callback::Retry(tx)))))
  .map(move |_| rx)
  - .map_err(|e| e.into_inner().0.take().expect("envelope not dropped").0)
  + .map_err(|mut e| (e.0).0.take().expect("envelope not dropped").0)
  }
  }
  @@ -142,7 +142,7 @@ impl<T, U> Receiver<T, U> {
  &mut self,
  cx: &mut task::Context<'_>,
  ) -> Poll<Option<(T, Callback<T, U>)>> {
  - match Pin::new(&mut self.inner).poll_next(cx) {
  + match self.inner.poll_recv(cx) {
  Poll::Ready(item) => {
  Poll::Ready(item.map(|mut env| env.0.take().expect("envelope not dropped")))
  }
  @@ -159,9 +159,8 @@ impl<T, U> Receiver<T, U> {
  }
  pub(crate) fn try_recv(&mut self) -> Option<(T, Callback<T, U>)> {
  - match self.inner.try_next() {
  - Ok(Some(mut env)) => env.0.take(),
  - Ok(None) => None,
  + match self.inner.try_recv() {
  + Ok(mut env) => env.0.take(),
  Err(_) => None,
  }
  }
  