This is just an example of async in Rust but it may be wrong. I would like to have something that executes in its own context without using a thread.

async_example.rs

use std::time::Duration;
use async_std::task;
use std::{thread, time};

// this is something that will take some time
// to execute so we execute it as an async function
// to not block the main thread. This function must not block
async fn do_sleep(val: u32) {
    task::sleep(Duration::from_secs(3)).await;
    println!("hello, world! {}", val);
}

// why main is not async? is it this ok?
// see https://book.async.rs/concepts/tasks.html
fn main() {
    let ten_millis = time::Duration::from_millis(2000);
    for i in 0..5 {
        // This function is similar to std::thread::spawn, except it spawns an asynchronous task
        // I do not care the value of this return
        task::spawn (
            async move {
                do_sleep(i).await
            }
        );
        println!("after async");
        // this simulates an external event in the main thread
        thread::sleep(ten_millis);
    };
}