google cloud functions - SigningError with Firebase getSignedUrl()

Question

I'm trying to use file.getSignedUrl() to get the download URL from Firebase Storage via Google Cloud Functions (Nodejs). I'm getting this error in the Cloud Functions console:

{ SigningError: A Forbidden error was returned while attempting to retrieve an access token for the Compute Engine built-in service account. This may be because the Compute Engine instance does not have the correct permission scopes specified. Permission iam.serviceAccounts.signBlob is required to perform this operation on service account projects/myapp-cd94d/serviceAccounts/[email protected].
    at SigningError (/user_code/node_modules/@google-cloud/storage/build/src/file.js:58:9)
    at authClient.sign.then.catch.err (/user_code/node_modules/@google-cloud/storage/build/src/file.js:1019:22)
    at process._tickDomainCallback (internal/process/next_tick.js:135:7) name: 'SigningError' }

I copied the code from the Add the Firebase Admin SDK to Your Server documentation. I have my serviceAccountKey.json in my functions folder. firebase deploy isn't given me the error

Error parsing triggers: Cannot find module 'serviceAccountKey.json'

so I must have the right path to my serviceAccountKey.json. I even generated a new private key, that didn't fix the problem. I have firebase-admin 6.1.0 and firebase-tools 6.1.0. Here's the relevant parts of my code:

const admin = require('firebase-admin');
var serviceAccount = require("./myapp-cd94d-firebase-adminsdk-1234x-sEcReT.json");

admin.initializeApp({
  credential: admin.credential.cert(serviceAccount),
  databaseURL: "https://myapp-cd94d.firebaseio.com"
});

...

const config = {
  action: 'read',
    expires: '03-17-2025'
  };

file.getSignedUrl(config).then(function(data) {
    const url = data[0];
    console.log(url);
  })
  .catch(function(error) {
    console.error(error);
  })

I saw that Doug Stevenson's answer has different code but it appears to be equivalent to the code in the documentation.

Answer 1

Waitting for answers