service.rs

trait Service<T, R>: Sink<SinkItem=(T, Sender<R>)> {
  fn call(&mut self, req: T) -> impl Future {
    let (tx, rx) = oneshot();
    match self.start_send((req, tx)) {
      Ok(Async::NotReady(e)) => { return Err(busy()).into_future() }
      Ok(Async::Ready) => { return rx; }
      Err(e) => { return Err(e).into_future() }
    }
  }
}