Create multiple timers at the same time, display exception

Create multiple timers at the same time, display exception
The previous timer will reset the time, and the next one will inherit the remaining time of the previous one

```dart
Widget _timerCountDown() {
return Countdown(
// controller: timerController,
seconds: 120,
build: (BuildContext context, double time) {
if (time < 5.0) {
return Text("ღ( ´・ᴗ・` )",style: TextStyle(color: Colors.white),);
}else{
return Text(time.toString(),style: TextStyle(color: Colors.white),);
}
},
interval: Duration(milliseconds: 100),
onFinished: () {
print('Timer is done!');
},
);
}
```