Function disposable_effect 

pub fn disposable_effect<K, F>(key: K, effect: F)
where
    K: PartialEq + 'static,
    F: FnOnce() -> DisposableEffectResult + 'static,

Runs effect after this call site enters the composition and again whenever key changes, and runs the cleanup it returned before the next run and when the call site leaves. Compose’s DisposableEffect.

disposable_effect(channel.clone(), move || {
    let subscription = subscribe(&channel);
    on_dispose(move || drop(subscription))
});