code: func (b *redisBroker) Publish(topic string, msg *broker.Message, opts ...broker.PublishOption) error {
  	v, err := b.opts.Codec.Marshal(msg)
  	if err != nil {
  		return err
  	}
  
  	conn := b.pool.Get()
  	_, err = redis.Int(conn.Do("PUBLISH", topic, v))
  	conn.Close()
  
  	return err
  }
docs: // Publish publishes a message.