ServerStreamInterceptor.go

type wrappedStream struct { 1
	grpc.ServerStream
}

func newWrappedStream(s grpc.ServerStream) grpc.ServerStream {
	return &wrappedStream{s}
}

func (w *wrappedStream) RecvMsg(m interface{}) error {
  ------
	return w.ServerStream.RecvMsg(m)
}


func (w *wrappedStream) SendMsg(m interface{}) error {
	-------
	return w.ServerStream.SendMsg(m)
}

func exampleServerStreamInterceptor(srv interface{}, ss grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
	
  // authentication (token verification)
	md, ok := metadata.FromIncomingContext(ss.Context())
	if !ok {
		return errMissingMetadata
	}
  
  /*
     auth logic, for instance check token in metadata
  */
  	  
  err := handler(srv, newWrappedStream(ss))
  
	return err
}


...
// Registering gRPC server with ServerInterceptor
s := grpc.NewServer(grpc.StreamInterceptor(exampleServerStreamInterceptor)) 
...