use future_bool::FutureBool;

#[tokio::main]
async fn main() {
    let run = FutureBool::new(false);
    let run_clone = run.clone();

    let task = tokio::spawn(async move {
        loop {
            // If run changes to false before `some_async_fn` is terminated, 
            // it will be interrupted.
            tokio::select! {
                _ = run_clone.wait_false() => break,
                _ = some_async_fn() => {}
            };
        }
    });

    // ... some other task sets run to false with 
    // `run.unset()`
    task.await;
}