fix message return before uuid write cause stuck (#203)

Co-authored-by: XingQiang Bai <[email protected]>

conn/channel.go

@@ -453,17 +453,24 @@ func (hc *channelSession) doRPCRequest(ctx context.Context, msg interface{}) (io
 		return nil, err
 	}
 	msgBytes := rpcMsg.Encode()
+
+	response := &channelResponse{Message: nil, Notify: make(chan interface{})}
+	hc.mu.Lock()
+	hc.responses[rpcMsg.uuid] = response
+	hc.mu.Unlock()
 	if hc.c == nil {
+		hc.mu.Lock()
+		delete(hc.responses, rpcMsg.uuid)
+		hc.mu.Unlock()
 		return nil, errors.New("connection unavailable")
 	}
 	_, err = hc.c.Write(msgBytes)
 	if err != nil {
+		hc.mu.Lock()
+		delete(hc.responses, rpcMsg.uuid)
+		hc.mu.Unlock()
 		return nil, err
 	}
-	response := &channelResponse{Message: nil, Notify: make(chan interface{})}
-	hc.mu.Lock()
-	hc.responses[rpcMsg.uuid] = response
-	hc.mu.Unlock()
 	<-response.Notify
 	hc.mu.Lock()
 	response = hc.responses[rpcMsg.uuid]