code: func MaxSendMsgSize(s int) client.Option {
  	return func(o *client.Options) {
  		if o.Context == nil {
  			o.Context = context.Background()
  		}
  		o.Context = context.WithValue(o.Context, maxSendMsgSizeKey{}, s)
  	}
  }
docs: //
  // MaxSendMsgSize set the maximum size of message that client can send.
  //