title: @google-cloud/express-oauth2-handlers not detecting required keys: GOOGLE_CLIENT_ID, GOOGLE_CLIENT_SECRET, GOOGLE_CALLBACK_URL, GCP_PROJECT
body: <p>I am trying to use @google-cloud/express-oauth2-handlers package in Firebase function to authorize user to then query google APIs.  </p>
  
  <p>I provided the required keys in client_secret.json file in  root directory of my function/app as per npm instructions for this package, however it's still not detecting the required keys from the json file. Its throwing me below error.</p>
  
  <pre><code>firebase deploy --only functions
  
  === Deploying to 'doppelganger-appl'...
  
  i  deploying functions
  i  functions: ensuring necessary APIs are enabled...
  ✔  functions: all necessary APIs are enabled
  i  functions: preparing functions directory for uploading...
  
  Error: Error occurred while parsing your function triggers.
  
  Error: Missing required keys: GOOGLE_CLIENT_ID, GOOGLE_CLIENT_SECRET, GOOGLE_CALLBACK_URL, GCP_PROJECT
  at exports.Provider.Provider.required (/Users/&lt;username&gt;/my-doppelganger-app/functions/node_modules/nconf/lib/nconf/provider.js:364:11)
  at Object.&lt;anonymous&gt; (/Users/&lt;username&gt;/my-doppelganger-app/functions/node_modules/@google-cloud/express-oauth2-handlers/config.js:53:7)
  at Module._compile (internal/modules/cjs/loader.js:776:30)
  at Object.Module._extensions..js (internal/modules/cjs/loader.js:787:10)
  at Module.load (internal/modules/cjs/loader.js:653:32)
  at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
  at Function.Module._load (internal/modules/cjs/loader.js:585:3)
  at Module.require (internal/modules/cjs/loader.js:690:17)
  at require (internal/modules/cjs/helpers.js:25:18)
  at Object.&lt;anonymous&gt; (/Users/&lt;username&gt;/my-doppelganger- 
  app/functions/node_modules/@google-cloud/express-oauth2- 
  handlers/tokenStorage.js:17:16)
  </code></pre>