如何使用passport-google-oauth20获取用户电子邮件

const GoogleStrategy = require('passport-google-oauth20').Strategy;

passport.use(new GoogleStrategy({
    clientID: GOOGLE_CLIENT_ID,
    clientSecret: GOOGLE_CLIENT_SECRET,
    callbackURL: "/auth/google/callback"
  },
  function(accessToken, refreshToken, profile, cb) {
    // 在这里可以获取用户的电子邮件信息
    const email = profile.emails[0].value;
    return cb(null, email);
  }
));

app.get('/auth/google',
  passport.authenticate('google', { scope: ['profile', 'email'] })
);

app.get('/auth/google/callback',
  passport.authenticate('google', { failureRedirect: '/login' }),
  function(req, res) {
    // 用户授权成功后的回调函数
    res.redirect('/');
  }
);

app.use(passport.initialize());
app.use(passport.session());

passport.serializeUser(function(user, cb) {
  cb(null, user);
});

passport.deserializeUser(function(user, cb) {
  cb(null, user);
});

function ensureAuthenticated(req, res, next) {
  if (req.isAuthenticated()) {
    return next();
  }
  res.redirect('/login');
}