select! example

use std::error::Error;
use futures::{future, select}; // futures-0.3.1
use futures::executor::block_on;

fn main() -> Result<(), Box<dyn Error>> {

    let ts: [(i32, i32); 3] = [(1, 10), (2, 20), (3, 30)];

    for t in &ts {
        let mut a = future::ready(t.0);
        let mut b = future::pending::<()>();
        block_on(async {
            let got = select! {
                    got = a => got + t.1,
                    _   = b => 0,
                };
            eprintln!("got, t.0, t.1: {} {} {}", got, t.0, t.1);
        })
    }
    Ok(())
}