code: func NewChangeWatchResp(ctx context.Context, message *DataChangeRequest, callback func(error)) *ChangeEvent {
  	return &ChangeEvent{
  		ctx:     ctx,
  		changes: []datasync.ProtoWatchResp{
  			&ChangeWatchResp{message: message},
  		},
  		callback: callback,
  	}
  }
docs: //go:generate protoc --proto_path=. --gogo_out=plugins=grpc:. datamsg.proto
  // NewChangeWatchResp is a constructor.