concurrency.rs

use futures::future::{Future, ok, select_ok}; // 0.1.26
use tokio; // 0.1.18
use tokio_timer::sleep; // 0.2.10
use std::time::Duration;

fn i() -> impl Future<Item=(), Error=()> {
    print!("Immediate\n");
    ok(())
}
fn d() -> impl Future<Item=(), Error=()> {
    sleep(Duration::from_millis(3000)).and_then(|_|{
        print!("Delayed\n");
        ok(())    
    }).map_err(|_| ())
}
fn main(){
    // Exits on completion of immediate and prints only Immediate
    // let fut = i().select(d()).then(|_| ok(()));
    // Waits for both the futures to complete and prints both Immediate and Delayed
    let fut = i().join(d()).map(|_| ());
    tokio::run(fut);
}