Memcache as driver in heroku environment

I have deployed my lumen application on heroku and I have enabled Memcache as an addon

on bash on heroku

php artisan dump-autoload

[RuntimeException] Could not establish Memcached connection.

Looking deeper I am puzzled that I have separate instance of memcache with username and password . Not sure where to give populate these setting for username and password as in cache.php . Or if I add these will be effective..

If you have any pointer please share

Regards