generator.rs

fn generate(num_chan: Sender<PipelineMsg>) {
    let mut num = 2;
    let _ = thread::Builder::new().spawn(move || {
        // Note the while condition,
        // Err will be returned by send when the corresponding receiver,
        // is dropped. That will result in this stage quitting.
        while let Ok(_) = num_chan.send(PipelineMsg::Generated(num)) {
            num = num + 1;
        }
    });
}