First process the pending messages in recv channel

Signed-off-by: Iceber Gu <wei.cai-nat@daocloud.io>

client.go

@@ -483,14 +483,22 @@ func (c *Client) dispatch(ctx context.Context, req *Request, resp *Response) err
 	}
 	defer c.deleteStream(s)
 
+	var msg *streamMessage
 	select {
 	case <-ctx.Done():
 		return ctx.Err()
 	case <-c.ctx.Done():
 		return ErrClosed
 	case <-s.recvClose:
+		// If recv has a pending message, process that first
+		select {
+		case msg = <-s.recv:
+		default:
 			return s.recvErr
-	case msg := <-s.recv:
+		}
+	case msg = <-s.recv:
+	}
+
 	if msg.header.Type == messageTypeResponse {
 		err = proto.Unmarshal(msg.payload[:msg.header.Length], resp)
 	} else {
@@ -502,4 +510,3 @@ func (c *Client) dispatch(ctx context.Context, req *Request, resp *Response) err
 
 	return err
 }
-}