// Cargo.toml: tokio = { version = "1", features = ["full"] }
use tokio::time::{sleep, Duration};

#[tokio::main]
async fn main() {
    let a = tokio::spawn(async {
        sleep(Duration::from_millis(100)).await;
        "a done"
    });
    let b = tokio::spawn(async {
        sleep(Duration::from_millis(50)).await;
        "b done"
    });

    println!("{} / {}", a.await.unwrap(), b.await.unwrap());
}