message: [bus] Update bus async trait usage test example.
diff: @@ -29,12 +29,12 @@ where
  #[async_trait::async_trait]
  pub trait Bus {
  - async fn subscribe<M: 'static>(&self, recipient: Recipient<M>) -> Result<()>
  + async fn subscribe<M: 'static>(self, recipient: Recipient<M>) -> Result<()>
  where
  M: Message + Send + Clone,
  M::Result: Send;
  - async fn broadcast<M: 'static>(&self, msg: M) -> Result<()>
  + async fn broadcast<M: 'static>(self, msg: M) -> Result<()>
  where
  M: Message + Send + Clone,
  M::Result: Send;
  @@ -83,7 +83,7 @@ where
  #[async_trait::async_trait]
  impl Bus for Addr<BusActor> {
  - async fn subscribe<M: 'static>(&self, recipient: Recipient<M>) -> Result<()>
  + async fn subscribe<M: 'static>(self, recipient: Recipient<M>) -> Result<()>
  where
  M: Message + Send + Clone,
  M::Result: Send,
  @@ -93,7 +93,7 @@ impl Bus for Addr<BusActor> {
  .map_err(|e| e.into())
  }
  - async fn broadcast<M: 'static>(&self, msg: M) -> Result<()>
  + async fn broadcast<M: 'static>(self, msg: M) -> Result<()>
  where
  M: Message + Send + Clone,
  M::Result: Send,
  @@ -120,7 +120,7 @@ mod tests {
  struct DoBroadcast {}
  #[derive(Debug, Message, Clone)]
  - #[rtype(result = "()")]
  + #[rtype(result = "Result<()>")]
  struct DoBroadcast2 {}
  struct MyActor {
  @@ -163,16 +163,12 @@ mod tests {
  }
  impl Handler<DoBroadcast2> for MyActor {
  - type Result = ();
  + type Result = ResponseActFuture<Self, Result<()>>;
  - fn handle(&mut self, _msg: DoBroadcast2, ctx: &mut Self::Context) {
  - // can not use async broadcast at here, lifetime error.
  - self.bus
  - //.broadcast(MyMessage {})
  - .send(Broadcast { msg: MyMessage {} })
  - .into_actor(self)
  - .then(|_result, act, _ctx| async {}.into_actor(act))
  - .wait(ctx);
  + fn handle(&mut self, _msg: DoBroadcast2, ctx: &mut Self::Context) -> Self::Result {
  + let f = self.bus.clone().broadcast(MyMessage {});
  + let f = actix::fut::wrap_future::<_, Self>(f);
  + Box::new(f)
  }
  }
  