Rust cow race

use std::{thread,time};
use std::sync::{Arc, RwLock};
use std::borrow::Cow;

fn main() {
    let mut list=Cow::from(vec![2,3,5,7,11,13,17]);
    let shared=Arc::new(RwLock::new(list.clone()));
    let h={
        let mut shared=shared.clone();
        thread::spawn(move || {
            let list_copy=shared.read().unwrap().clone();
            println!("{:?}", list_copy);
        })
    };
    list.to_mut().push(19);
    //Comment the sleep line and the other thread should get the new list.
    thread::sleep(time::Duration::from_millis(10));
    *shared.write().unwrap()=list.clone();
    h.join().unwrap();
}