Here is a web application with a sign-in system, built with advanced Node.js and Express.js.
With authentication, which is the act of verifying the identity of a person or process, in order to implement the sign-in system safely.

As a registered user, they can login and logout.
As a user, they can register then logging in as the new user.
As a user, they can login using a Github account into the chat room. Send and display massages to all online users.
As a login user, they can be announced by the application who has entered or left the chat.