Fix review

protocol/dubbo/listener.go

@@ -331,16 +331,15 @@ func (h *RpcServerHandler) OnCron(session getty.Session) {
 	}
 }
 
-// rebuild the context by attachment.
+// rebuildCtx rebuild the context by attachment.
 // Once we decided to transfer more context's key-value, we should change this.
 // now we only support rebuild the tracing context
 func rebuildCtx(inv *invocation.RPCInvocation) context.Context {
 	ctx := context.Background()
 
-	// actually, if user do not use any opentracing framework, it will always be error.
+	// actually, if user do not use any opentracing framework, the err will not be nil.
 	spanCtx, err := opentracing.GlobalTracer().Extract(opentracing.TextMap,
 		opentracing.TextMapCarrier(inv.Attachments()))
-
 	if err == nil {
 		ctx = context.WithValue(ctx, constant.TRACING_REMOTE_SPAN_CTX, spanCtx)
 	}