async function printDocTitle(auth) {
  const docs = google.docs({version: 'v1', auth});
  const res = await docs.documents.get({
    documentId: '195j9eDD3ccgjQRttHhJPymLJUCOUjs-jmwTrekvdjFE',
  });
  console.log(`The title of the document is: ${res.data.title}`);
}
Prints the title of a sample doc:
https://docs.google.com/document/d/195j9eDD3ccgjQRttHhJPymLJUCOUjs-jmwTrekvdjFE/edit
@param {google.auth.OAuth2} auth The authenticated Google OAuth 2.0 client.