Function spawn_interval 

pub fn spawn_interval<S, F, R>(
    s: S,
    period: Duration,
    fun: F,
) -> impl Lifecycle<S = IntrospectableStop>
where
    S: Clone + 'static + Send + Sync,
    F: Fn(S) -> R + Send + Sync + 'static,
    R: Future<Output = ()> + Send,