Provide Send Futures

This would be better with rust-lang/rust#63063

Author: jonhoo

src/multiplex/client.rs

@@ -81,11 +81,11 @@ where
     NT::Item: 'static + Send,
     NT::SinkError: 'static + Send + Sync,
     NT::Error: 'static + Send + Sync,
-    NT::Future: 'static,
+    NT::Future: 'static + Send,
 {
     type Error = SpawnError<NT::MakeError>;
     type Response = Client<NT::Transport, Error<NT::Transport, Request>, Request>;
-    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>>>>;
+    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>> + Send>>;
 
     fn call(&mut self, target: Target) -> Self::Future {
         let maker = self.t_maker.make_transport(target);
@@ -349,7 +349,7 @@ where
 {
     type Response = T::Ok;
     type Error = E;
-    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>>>>;
+    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>> + Send>>;
 
     fn poll_ready(&mut self, cx: &mut Context) -> Poll<Result<(), E>> {
         Poll::Ready(ready!(self.mediator.poll_ready(cx)).map_err(|_| E::from(Error::ClientDropped)))

src/pipeline/client.rs

@@ -60,11 +60,11 @@ where
     NT::Item: 'static + Send,
     NT::SinkError: 'static + Send + Sync,
     NT::Error: 'static + Send + Sync,
-    NT::Future: 'static,
+    NT::Future: 'static + Send,
 {
     type Error = SpawnError<NT::MakeError>;
     type Response = Client<NT::Transport, Error<NT::Transport, Request>, Request>;
-    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>>>>;
+    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>> + Send>>;
 
     fn call(&mut self, target: Target) -> Self::Future {
         let maker = self.t_maker.make_transport(target);
@@ -308,7 +308,7 @@ where
 {
     type Response = T::Ok;
     type Error = E;
-    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>>>>;
+    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>> + Send>>;
 
     fn poll_ready(&mut self, cx: &mut Context) -> Poll<Result<(), E>> {
         Poll::Ready(ready!(self.mediator.poll_ready(cx)).map_err(|_| E::from(Error::ClientDropped)))