c.call(0);
let mut count: usize = 0;
c.register(Box::new(move |val| { count = count+1; println!("Callback 2, {}. time: {}", count, val); } ));
c.call(0);
let mut count: usize = 0;
c.register(Box::new(move |val| { count = count+1; println!("Callback 2, {}. time: {}", count, val); } ));