static void Main(string[] args)
{
ChatRoom chatRoom = new ChatRoom();
User user1 = new User("user1");
User user2 = new User("user2");
User user3 = new User("user3");
chatRoom.Register(user1);
chatRoom.Register(user2);
chatRoom.Register(user3);
chatRoom.Send("hello", user1, user2);
user1.Send(user2, "hello 2");
Console.WriteLine(" ");
chatRoom.SendAll("hello all");
}
