Run the endless loop and quit when the user types ':quit'.

endless_loop_with_quit.rs

use std::io::{BufRead};

fn main() {
    println!("Type :quit<Enter> to quit this program.");
    let stdin = std::io::stdin();
    loop {
        let line = stdin.lock().lines().next().unwrap().unwrap();
        match line.as_ref() {
            ":quit" => std::process::exit(0),
            _ => { break }
        }
    }
}