toTopic method
Adds a new subscription topic with the AtMostOnce Qos Level. If you want to change the Qos level follow this call with a call to AtTopic(MqttQos).
Implementation
MqttSubscribeMessage toTopic(String topic) {
_lastTopic = topic;
payload.addSubscription(topic, MqttQos.atMostOnce);
return this;
}