The example in the concurrency guide is incorrect

[reem]

The offending example is:

use std::thread::Thread;

fn main() {
    for _ in 0..10 {
        Thread::spawn(|| {
            println!("Hello World!");
        });
    }
}

With the new detaching thread semantics, this is incorrect since main can exit before all the detached threads have printed.

[steveklabnik]

I think that this was in the intro as well.