rs-hello

Demo Rust hello server from Rust book. Contains collection of Rust design patterns:

• create OS native threads with std::thread;
• thread communication with std::sync::mpsc channel;
• use Arc<Mutex<...>> for safe share receiver end between threads (use channel as shared queue);
• passing job closure to worker theads (use trait object type Box<dyn FnOnce() + Send + 'static> for it);
• simple use Tcp Listener;
• use Option<...> enum to take() some value from mutable self reference (move JoinHandler value from self to join());
• use type alias;
• impl Drop trait for gracefull shutdown.