How to modify the returned metadata

[baozi-2019]

I want to add error message to returned metadata,but it does not work.This is my code.

func ErrorServerInterceptor(ctx context.Context, req any, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (resp any, err error) {
	resp, err = handler(ctx, req)
	if err != nil {
		data := make(map[string]string)
		data["exceptionResult"] = err.Error()
		errorMessage := &grpc_message.ErrorMessage{
			ServiceName: ServiceName,
			Reason:      err.Error(),
			Metadata:    data,
		}
		//incomingContext, _ := metadata.FromIncomingContext(ctx)
		bytes, _ := json.Marshal(errorMessage)
		md, ok := metadata.FromOutgoingContext(ctx)
		if !ok {
			md = metadata.New(map[string]string{})
		}
		md.Append("custom-key", string(bytes))
		ctx = metadata.NewOutgoingContext(ctx, md)
		return nil, nil
	}
	return resp, err
}

[purnesh42H]

@aranjans you can assign it to me

[purnesh42H]

@baozi-2019 could you provide more context on why you are not returning the error (returning nil) from your interceptor?

[purnesh42H]

@baozi-2019 you need to return a non-nil error in order to add the error message to the metadata