private static void subscribe() throws MqttException {
        IMqttToken mqttToken = mqttClient.subscribe(TOPIC, QOS);
        mqttToken.waitForCompletion(WAIT_FOR_COMPLETION);
    }
@author Younsung Hwang
@author Taejin Koo
agent-module/plugins-it/paho-mqtt-it/src/test/java/com/navercorp/pinpoint/it/plugin/paho/mqtt/PahoMqttV3ClientIT.java