periodicTimer function
Implementation
TimerGenerator periodicTimer(Duration interval,
{Duration alignment = Duration.zero}) {
assert(interval > Duration.zero);
DateTime? next;
return (DateTime now) {
next = alignDateTime((next ?? now).add(interval), alignment);
if (now.compareTo(next!) < 0) {
next = alignDateTime(now.add(interval), alignment);
}
return next!;
};
}