Need help or a tutorial for SWIFT to API

I have made my self a API using PHP, rest and jwt. User and registration with name, password and email. This is the guide for that API. I understand that it is best/more easy to use firebase or similar, but i want to learn myself and have the data. Can somebody help med with a tutorial or example? I want a segue screen with login, and auto login using token. If the token is wrong automaticly coming to register or login. KR

From the client to serverside - if somebody have another good API with client code from swift.