#326 fix the issue that errors have been overrided

server/server.go

@@ -422,10 +422,12 @@ func (s *Server) serveConn(conn net.Conn) {
 						res.Metadata = resMetadata
 					} else {
 						for k, v := range resMetadata {
+							if meta[k] == "" {
 								meta[k] = v
 							}
 						}
 					}
+				}
 
 				if len(res.Payload) > 1024 && req.CompressType() != protocol.None {
 					res.SetCompressType(req.CompressType())