Continuously reads stdin from own stdout

stdin.rs

use std::{
    io::{self, BufRead, Write},
    thread,
    time::{Duration, SystemTime, UNIX_EPOCH},
};

fn main() {
    // Spawn a thread that continuously reads stdin
    thread::spawn(|| {
        let stdin = io::stdin();
        for line in stdin.lock().lines() {
            match line {
                Ok(text) => eprintln!("stdin: {}", text),
                Err(_) => break,
            }
        }
    });

    let stdout = io::stdout();
    let mut out = stdout.lock();

    loop {
        let now = SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .unwrap()
            .as_millis();

        writeln!(out, "{}", now).unwrap();
        out.flush().unwrap();

        thread::sleep(Duration::from_millis(1000));
    }
}