Note: you have to implement these instructions in the user app only.
For Google authentication, we need to add a little iOS configuration.
You have to go Info.plist and search for:
<string>com.googleusercontent.apps.279585014161-lnc442tn9o8m76nfo3vr2tnn14l844oi</string> and replace the URL with the one that you will find in GoogleService-Info.plist under: <key>REVERSED_CLIENT_ID</key>