title: How to implement native 'Sign In with Apple' flow
body: <p>I’ve got a question about implementing Sign In With Apple. I am newbie in Apple development so the question might be trivial.</p>
  
  <p>My app consists of two parts - backend part written in Go and iOS/Android/browser clients. So all user management obviously happens at the backend side. Users can register and sign in by email etc. Clients just send login/email and password to backend, nothing unusual.</p>
  
  <p>Some time ago I decided to implement Apple Sign In as an option to users who have Apple ID to register/login. I implemented it with WebView in Android following this instruction <a href="https://developer.okta.com/blog/2019/06/04/what-the-heck-is-sign-in-with-apple" rel="nofollow noreferrer">https://developer.okta.com/blog/2019/06/04/what-the-heck-is-sign-in-with-apple</a> for browsers, Android and iOS &lt; 13.0 and it works really well. After successful login a call from Apple to backend redirect URI happens and then backend handles user data and makes calls to clients to refresh page etc.</p>
  
  <p>But then I made native implementation of Sign In With Apple in iOS >= 13.0. I followed this instruction <a href="https://developerinsider.co/ios-13-how-to-integrate-sign-in-with-apple-in-your-application/" rel="nofollow noreferrer">https://developerinsider.co/ios-13-how-to-integrate-sign-in-with-apple-in-your-application/</a> to implement it and authentication happens at Apple side well but then it just returns user data to Swift and that’s all.  I can’t figure out how to tell backend that login is done. Can anybody tell me how to include backend in the flow? Thank you.</p>