[GitHub] [dubbo-go] lethexixin commented on issue #1410: grpc Context failed to transfer data

[GitBox <gi...@apache.org>]

lethexixin commented on issue #1410:
URL: https://github.com/apache/dubbo-go/issues/1410#issuecomment-904694063


   @xavier-niu 谢谢，查资料才发现在 grpc 中，client 与 server 之间通过 context 传递上下文数据的时候，不能使用 context.WithValue，因为 server 端无法获取到 client 自定义的 key， 不过我们可以使用 grpc 提供的 medadata 接口：
   ```golang
   //客户端:   
   func main() {
           req := &demo.Req{}
   	res := &demo.Res{}
   	ctx := metadata.NewOutgoingContext(context.Background(), metadata.Pairs("socket.addr", "127.0.0.1:12788"))
   	err := consumer.GetContextImpl().FContext(ctx, req, res)
   }
   
   //服务端:
   func (g *Provider) FContext(ctx context.Context, req *demo.Req) (res *demo.Res, err error) {
   	if md, ok := metadata.FromIncomingContext(ctx); ok {
   		xIds := md.Get("socket.addr")
   		fmt.Println("xIds:",xIds)
   	}
   	return
   }
   ```
   **如此，服务端就可以拿到context的值了，不过这个metadata方式只能传string类型**  
   
   
   
   参考：https://mp.weixin.qq.com/s/cwkfYA2rgNIbHom5Yoeizg
   ![image](https://user-images.githubusercontent.com/46220496/130634071-7e49c399-642b-480b-aab5-69ef649cc56c.png)
   
   
   **最后：或许可以在 [dubbo-go-samples/context](https://github.com/apache/dubbo-go-samples/tree/master/context) 模块的readme.md 文件中描述一下grpc中关于context的问题及解决方案，避免别的小伙伴入坑😳**


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