code: func (*GreeterService) SayHello(ctx context.Context, request *helloworld.HelloRequest) (*helloworld.HelloReply, error) {
  	if request.Name == "" {
  		return nil, errors.New("not filled name in the request")
  	}
  
  	logging.Infof("Greeting client: %v", request.Name)
  
  	return &helloworld.HelloReply{Message: "Greetings " + request.Name}, nil
  }
docs: // SayHello returns error if request.name was not filled otherwise: "hello " + request.Name