printDuration function
Implementation
String printDuration(Duration duration) {
String twoDigits(int n) => n.toString().padLeft(2, "0");
String twoDigitMinutes = twoDigits(duration.inMinutes.remainder(60));
String twoDigitSeconds = twoDigits(duration.inSeconds.remainder(60));
return "$twoDigitMinutes:$twoDigitSeconds";
}