code: func sendMessage(producer *client.SyncProducer, msg utils.Message) error {
  	var (
  		msgKey   []byte
  		msgValue []byte
  	)
  
  	// init message
  	if msg.Key != "" {
  		msgKey = []byte(msg.Key)
  	}
  	msgValue = []byte(msg.Text)
  
  	// Demonstrate the use of SyncProducer.SendMsgByte() API.
  	// The function doesn't return until the delivery status is known.
  	_, err := producer.SendMsgByte(msg.Topic, msgKey, msgValue)
  	if err != nil {
  		logrus.DefaultLogger().Errorf("SendMsg Error: %v", err)
  		return err
  	}
  	fmt.Println("message sent")
  	return nil
  }
docs: // sendMessage demonstrates SyncProducer.SendMsgByte API to publish a single
  // message to a Kafka topic.