Code shared from the Rust Playground

playground.rs

use std::{
    sync::{Arc, Mutex},
    thread,
};

struct Test {
    flag: bool,
}

impl Test {
    fn new() -> Self {
        let test = Test { flag: false };
        test
    }

    fn check_flag(&self) -> bool {
        println!("flag {}", &self.flag);
        return self.flag;
    }

    fn set_flag(&mut self) {
        println!("set flag");
        self.flag = true
    }
}

fn main() {
    let test = Arc::new(Mutex::new(Box::new(Test::new())));
    let test2 = test.clone();

    thread::spawn(move || {
        thread::sleep_ms(1500);
        println!("set");
        test2.lock().expect("thread 1").set_flag();
    });

    loop {
        let flag = test.lock().expect("main 1").check_flag();
        thread::sleep_ms(500);
        if flag {
            break;
        }
    }

    println!("end");
}