Cancelable Spawned Coroutines in Verse (advanced version)

routine.verse

<#> Usage
    MyRoutine := SpawnRoutine(SomeLongRunningTask)
    MyRoutine.Cancel()

SpawnRoutine<public>(Func : type{_()<suspends>:void}):routine = 
    Routine := routine{Func := Func}
    Routine.Start()
    return Routine

routine<public> := class():
    Func<public> : type{_()<suspends>:void} 
    Event<protected> : event() = event(){}
    var MaybeTask<protected> : ?task(void) = false 
    var _IsRunning<protected> : logic = false

    Start<internal>():void = 
        Task := spawn {RunRoutine()}
        set MaybeTask = option {Task}

    RunRoutine<protected>()<suspends>: void = 
        set _IsRunning = true
        race:
            Func()
            Event.Await()
        set _IsRunning = false

    Cancel<public>():void = Event.Signal()

    GetTask<public>()<decides><transacts>:task(void) = MaybeTask?

    IsRunning<public>()<decides><transacts>:void = _IsRunning?