title: Google Sign-In: exchange code for access token and ID token
body: <p>I am using client ID for Android/iOS to authenticate users with Google Sign-In. This is working fine and I receive a code after successful authentication.</p>
  
  <p>Now for some reason I would like to validate this code in the server-side with google and obtain access token. But we do not have any secret key for client ID(s) for Android/iOS. How can I verify the code and get the access token?</p>