I need to read the list of users (and groups) from my google domain.
So I went to my Google APIs Console and enabled Admin SDK and created a
you can go to "security" settings in the admin console (admin.google.com/AdminHome?chromeless=1&pli=1#SecuritySettings:); then click on advance settings > Manage third party OAuth Client access. After this map your client id(generated from appconsole code.google.com/apis/console under API access for oath2) and "One or More API Scopes". Use comma separated scopes as mentioned there. For google directory you can use https://www.googleapis.com/auth/admin.directory.group,https://www.googleapis.com/auth/admin.directory.user
Hope after this it works :)