Code shared from the Rust Playground

playground.rs

use futures::{StreamExt as _, stream};
use tokio::time::sleep;
use tokio::time::{Instant, Duration};

async fn loopnprint(name: &str) -> Result<(), String> {
    let now = Instant::now();
    loop {
        sleep(Duration::from_millis(101)).await;
        let elapsed = Instant::now() - now;
        if name == "task2" && elapsed > Duration::from_millis(1230) {
            return Err("OHNO".to_string());
        }
        println!("name: {name}, delayed: {:?}.", elapsed);
    }
}

async fn and_loop() -> Result<(), String> {
    let mut s = stream::FuturesUnordered::new();

	s.push(loopnprint("task2"));
	s.push(loopnprint("task0"));
	s.push(loopnprint("task1"));


    while let Some(f) = s.next().await {
         return f;
    }
    Ok(())
}

#[tokio::main]
async fn main() {
    let ret = and_loop().await;
    println!("RET: {:?}", ret);
    sleep(Duration::from_millis(1000)).await;
    println!("There should be no more prints!");
}