title: Export GitLab CI variables to json file
body: <p>I have a nodejs repository in gitlab service and I use gitlab CI runner with docker. I need to output some GitLab CI variables (like CI_JOB_ID or CI_COMMIT_TAG) directly to node app. Using gitlab http api is not good for me. I need to store that information to any.json file right after build process. How to implement it?</p>