getTokenInfo

const oauth2Client = new OAuth2Client({
    clientId: '1',
    clientSecret: 'G',
    redirectUri: "https://developers.google.com/oauthplayground",
});

const url = oauth2Client.generateAuthUrl({
    access_type: 'offline',
    scope: ['https://www.googleapis.com/auth/gmail.send'],
});

const code = '4/0'; // Copia el código de autorización obtenido después de la autorización.


// After acquiring an access_token, you may want to check on the audience, expiration,
// or original scopes requested.  You can do that with the `getTokenInfo` method.
const tokenInfo = await oauth2Client.getTokenInfo(
    oauth2Client.credentials.access_token
);
console.log(tokenInfo);