Using Google Drive API from cloud function using the default service account without generating a key

As far as I know one best practice on Google Cloud is to not use Service Account keys as much as possible.

Here I have a Google Cloud function (nodejs) accessing Drive via Drive API (googleapis package v95.0.0), using a service account key (generated file via console).

What works:

const settings = require('./config/driveSA.json');
const options = {
         googleKey: settings,
         user: 'test@test.com' //user impersonification
}

const auth = gdriveUtils.prepareJwt(google, options);

const drive = google.drive({ version: 'v3', auth: auth });

const file = await drive.files.get({
    fileId: fileId,
    alt: 'media',
    supportsTeamDrives: true,
});

What I want to achieve:

I want to improve this function, making it directly use the default service account inherited by the Cloud Function itself (which is the same referred by the key).

This approach always works when using '@google-cloud' related packages. Like for Storage we can simply:

const storage = new Storage();
const bucket = storage.bucket(bucketName);

What I tried:

Without specifying any auth obj:

const drive = google.drive({ version: 'v3' });

const file = await drive.files.get({
    fileId: fileId,
    alt: 'media',
    supportsTeamDrives: true,
});

Using a not-really-documented method: getApplicationDefault

import { GoogleApis, Auth } from 'googleapis';
const adcResponse = await google.auth.getApplicationDefault();
const auth: Auth.GoogleAuth = new google.auth.GoogleAuth(adcResponse);
const drive = google.drive({ version: 'v3', auth: auth });

const file = await drive.files.get({
    fileId: fileId,
    alt: 'media',
    supportsTeamDrives: true,
});

Unfortunately the package's documentation is always vague about the authentication part and always use keys in the examples. Is this something viable? Or am I forced to use a key in this case?

Thanks!