khadinakbarlabs/expo-mobile-app-builder/add-google-signin-credential-manager

npm exec --no -- expo install @react-native-google-signin/google-signin

{
  "expo": {
    "plugins": [
      ["@react-native-google-signin/google-signin", {
        "iosUrlScheme": "com.googleusercontent.apps.YOUR_CLIENT_ID"
      }]
    ]
  }
}

import { GoogleSignin, statusCodes } from '@react-native-google-signin/google-signin';
GoogleSignin.configure({
  webClientId: 'YOUR_WEB_CLIENT_ID.apps.googleusercontent.com',
});
const signIn = async () => {
  try {
    await GoogleSignin.hasPlayServices();
    const userInfo = await GoogleSignin.signIn();
    // userInfo.idToken — send to backend for verification
  } catch (e: any) {
    if (e.code === statusCodes.SIGN_IN_CANCELLED) return;
    throw e;
  }
};

import { OAuth2Client } from 'google-auth-library';
const client = new OAuth2Client();
const ticket = await client.verifyIdToken({ idToken, audience: WEB_CLIENT_ID });
const payload = ticket.getPayload();
// payload.sub = stable Google user ID