countdown library Null safety

Classes

Countdown<T>
Countdown to a given completion DateTime. [...]
CountdownController<T>
Controller to manage a Countdown and its CountdownEvents
CountdownMilestone<T>
Countdown to an mielstone occurring at a specific duration from the completion of a parent Countdown
CountdownRepeat
Condition under which a countdown is to be repeated
RaceDayController
Controller for managing countdown to race day and its events
RaceDayEvents
Events occurring on or around race day