timerData function
Implementation
String timerData(){
countdownDuration = Duration(hours: int.parse("00"), minutes: int.parse("00"), seconds: int.parse("00"));
timer = Timer.periodic(Duration(seconds: 1), (_) => addTime());
String twoDigits(int n) => n.toString().padLeft(2, '0');
final hours = twoDigits(duration.inHours);
final minutes = twoDigits(duration.inMinutes.remainder(60));
final seconds = twoDigits(duration.inSeconds.remainder(60));
return "$hours";
}