Mqtt.fromJson constructor
Implementation
Mqtt.fromJson(Map<String, dynamic> json) {
if (json["channel"] is String) this.channel = json["channel"];
if (json["clientId"] is String) this.clientId = json["clientId"];
if (json["username"] is String) this.username = json["username"];
if (json["password"] is String) this.password = json["password"];
}