public async Task Handle(TrafficLightStateMachine light)
{
TraceHelper.Log(nameof(RedState)).Invoke();
await Task.Delay(2000);
// await light.MoveNext(new GreenState());
}
internal static IO <Task <TrafficLightState> > GreenState
() =>
from _ in TraceHelper.Log(nameof(GreenState))
select(from __ in Task.Delay(TimeSpan.FromSeconds(3))
select new TrafficLightState(YellowState));
internal static IO <Task <TrafficLightState> > RedState
() =>
from _ in TraceHelper.Log(nameof(RedState))
select(from __ in Task.Delay(TimeSpan.FromSeconds(2))
select default(TrafficLightState));
