I'm trying to simply test for an existence of a file on our Google Cloud Platform (GCP) storage. I'm using GCP buckets on express js servers. Below is essentially a very simple exampled copied off of https://googleapis.dev/nodejs/storage/latest/File.html#exists

EDIT: This is how I authenticate the GCP key:

const { Storage } = require('@google-cloud/storage');

const storage = new Storage({
    projectId: 'my-cloud',
    keyFilename: process.env.GOOGLE_APPLICATION_CREDENTIALS,
});
const bucketName = 'my-ci';

(With small changes, I realise you are supposed to return data[0])

const bucket = storage.bucket(bucketName);
const file = bucket.file(path);
const exists = await file.exists().then(data => {
    return data
})

But when I try run this, I get the error:

[nodemon] starting `node --inspect server/server.js`
Debugger listening on ws://127.0.0.1:9229/9a677766-4a93-4499-b57c-55f5f05096d7
For help, see: https://nodejs.org/en/docs/inspector
Server listening on port 4000!
/opt/node_modules/jwa/index.js:115
return new TypeError(errMsg);
^

TypeError: key must be a string, a buffer or an object
at typeError (/opt/node_modules/jwa/index.js:115:10)
at checkIsPrivateKey (/opt/node_modules/jwa/index.js:61:9)
at Object.sign (/opt/node_modules/jwa/index.js:147:5)
at Object.jwsSign [as sign] (/opt/node_modules/jws/lib/sign-stream.js:32:24)
at JWTAccess.getRequestHeaders (/opt/node_modules/google-auth-library/build/src/auth/jwtaccess.js:87:31)
at JWT.getRequestMetadataAsync (/opt/node_modules/google-auth-library/build/src/auth/jwtclient.js:76:51)
at JWT.getRequestHeaders (/opt/node_modules/google-auth-library/build/src/auth/oauth2client.js:238:37)
at GoogleAuth.authorizeRequest (/opt/node_modules/google-auth-library/build/src/auth/googleauth.js:593:38)
at processTicksAndRejections (node:internal/process/task_queues:96:5)

Since the error message did not give a useful traceback, I did some digging on my own. Through putting console.log statements everywhere, I narrowed it down to the line

const exists = await file.exists().then(data => {
    return data
})

and tried various approaches from removing the .then(...) clause, to removing the await (which, does work until the promise is resolved). None of these seemed to have worked.

What may be potential causes of this?