Yielding Async Tasks via Custom Waker Wakeups

use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll};
 
struct YieldOnce {
    yielded: bool,
}
 
impl Future for YieldOnce {
    type Output = ();
 
    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        if self.yielded {
            Poll::Ready(())
        } else {
            self.yielded = true;
            cx.waker().wake_by_ref();
            Poll::Pending
        }
    }
}
 
async fn execute_cooperative_task() -> i32 {
    let mut sum = 0;
    for i in 0..10 {
        sum += i;
        if i % 3 == 0 {
            YieldOnce { yielded: false }.await;
        }
    }
    sum
}