Nodejs selenium-webdriver firefox proxy authentication

We need a sample nodejs script which is working with *selenium-webdriver/firefox* and proxy like 'http://user:pass@ip:port'.

selenium-webdriver/firefox works great with proxy 'http://ip:port' but it does not support the Proxy Basic Authentication with user:pass. it's a known bug: https://github.com/seleniumhq/selenium/issues/1802

NOTE it should work with the latest firefox 68
NOTE we don't want to use 'proxy-chain' b/c it's taking resources and slow. We need another solution.

You need to have one test proxy with user:pass and you need send us the working code.