スレッド間通信をchannelからmutexへ(@Rust)

use std::sync::{Mutex, Arc};
use std::thread;
use std::time::Duration;
//use std::sync::mpsc;

fn main() {
    //let (tx, rx) = mpsc::channel();
    let count = Arc::new(Mutex::new(0));
    let mut handles = Vec::new();

    for i in 0..3 {
        //let thread_tx = tx.clone();
        let count = Arc::clone(&count);
        let handle = thread::spawn(move || {
            for j in 1..10 {
                println!("hi number {} {} from the spawned thread!", i, j);
                thread::sleep(Duration::from_millis(1));
            }
            //thread_tx.send(i).unwrap();
            let mut num = count.lock().unwrap();
            *num += 1;
        });
        handles.push(handle);
    }

    for i in 1..5 {
        println!("hi number {} from the main thread!", i);
        thread::sleep(Duration::from_millis(1));
    }

    for handle in handles {
        handle.join().unwrap();
    }

    //drop(tx);       // without drop(), this program doesn't terminate, wait for tx forever
/* 
    for received in rx {
        println!("Got from the threads : {}", received);
    }
*/
    println!("Result: {}", *count.lock().unwrap());

}