example.rs

let keep_running = Rc::new(Cell::new(true));

let kr = keep_running.clone(); // there are now two objects pointing to the same place
                               // the ownership of this copy is passed to the task.
let background_printer = Task::local(async move {
    while kr.get() {
       sleep(Duration::from_millis(100)).await;
    }
});

sleep(Duration::from_seconds(2)).await;
keep_running.set(false);

background_printer.await;