Can't sign in to Discourse with GitLab plugin

Hello,

I am using a plugin from GitLab to sign into Discourse https://gitlab.com/gitlab-org/discourse-omniauth-gitlab, but I keep getting error 500 even though I followed the instructions precisely. What could be wrong?

My config in Discorse:
GITLAB_URL: http://0.0.0.0 (I don’t have a domain name yet)

hooks:
  after_code:
    - exec:
        cd: $home/plugins
        cmd:
          - git clone https://github.com/discourse/docker_manager.git
          - git clone https://gitlab.com/gitlab-org/discourse-omniauth-gitlab.git

Callback URL in GitLab:
http://DISCOURSE_URL/auth/gitlab/callback

:question:

Use the real IP of GitLab, I don’t think that will work.