title: Getting a Google OAuth access token from an id_token
body: <p>I'm using Google authentication with the redirect_uri option (to avoid the pop-up). When the user signs in to Chrome I can get an access token, but in Safari (for example), I can't figure out how to get an access token. The redirect querystring includes an id_token, which I can successfully verify using this endpoint:</p>
  
  <pre><code>https://www.googleapis.com/oauth2/v3/tokeninfo?id_token=XYZ123
  </code></pre>
  
  <p>This gives me some info about the user, but what I really want is an access token since my backend API expects it.</p>
  
  <p>Can I get an access token from an id_token? If so, how. I can't find any examples.</p>
  
  <p>Clarification: I'm not trying to authenticate my app, I'm getting the id_token from the user authenticating via Google sign in on the front-end.</p>