public override async Task OnDisconnectedAsync(Exception exception)
{
var user = _connections.GetUser(Context.ConnectionId);
if (user != null)
{
var chatRoom = _connections.GetRoom(Context.ConnectionId);
_connections.Remove(Context.ConnectionId);
await Clients.Group(chatRoom).SendAsync("UserLeft", user);
}
await base.OnDisconnectedAsync(exception);
}
