chrome.identity.getAuthToken not working

Question

I am working with Chrome Identity API, to provide users with a Google Authentication on my Chrome Extension.

I followed the official tutorial of Google : link Chrome Id

Answer 1

The accepted answer is incorrect. You can upload it to the webstore, publish it, then install it from the webstore. After installing, find the installed extension app dir (~/Library/Application\ Support/Google/Chrome/Default/Extensions/ on a mac), and copy the key key from the installed manifest.json into your source code manifest.json. After adding the key field to your manifest.json, your app id will not change during local development.

Source: https://developer.chrome.com/apps/app_identity#copy_key