Why does print!() not work in a loop?

print_macro_in_loop.rs

fn main() {
    loop {
        print!(".");
        ::std::thread::sleep(::std::time::Duration::from_millis(1000));
    }
}

Solution from @sebk from irc.mozilla.org#rust

11:51 Why does print!() not work in a loop? https://gist.github.com/zzeroo/95b438c321bb930d3bbf13c59c64dfed
11:52 zzeroo: stdout is probably linebufferd
11:52 so unless you send \n nothing will actually be send out
11:53 Ah without thread::sleep it works... danm lazyness ><
11:53 add std::io::stout().flush() to the loop and it should work
11:57 https://is.gd/mE7eRk

use std::io::Write;

fn main() {
    loop {
        print!(".");
        std::io::stdout().flush();
        std::thread::sleep(std::time::Duration::from_millis(1000));
    }
}