timestamp property Null safety
Implementation
String get timestamp{
final DateTime _now = DateTime.now();
return _now.year.toString() + _now.month.toString().padLeft(2, '0') + _now.day.toString().padLeft(2, '0') + _now.hour.toString().padLeft(2, '0') + _now.minute.toString().padLeft(2, '0') + _now.second.toString().padLeft(2, '0');
}