Gitlab in Docker not working on subdomain

I’ve installed Gitlab-CE inside a Docker container. When I activate the container, Gitlab is accessible on my domain, but not on the subdomain I set in the config.

My config is as follows:

version: '3'

services:
  gitlab:
    image: 'gitlab/gitlab-ce'
    restart: always
    hostname: 'gitlab.mydomain.com'
    links:
      - postgresql:postgresql
      - redis:redis
    environment:
      GITLAB_OMNIBUS_CONFIG: |
        postgresql['enable'] = false
        gitlab_rails['db_username'] = "gitlab"
        gitlab_rails['db_password'] = "gitlab"
        gitlab_rails['db_host'] = "postgresql"
        gitlab_rails['db_port'] = "5432"
        gitlab_rails['db_database'] = "gitlabhq_production"
        gitlab_rails['db_adapter'] = 'postgresql'
        gitlab_rails['db_encoding'] = 'utf8'
        redis['enable'] = false
        gitlab_rails['redis_host'] = 'redis'
        gitlab_rails['redis_port'] = '6379'
        external_url 'http://gitlab.mydomain.com:30080'
        gitlab_rails['gitlab_shell_ssh_port'] = 30022
    ports:
      # both ports must match the port from external_url above
      - "30080:30080"
      # the mapped port must match ssh_port specified above.
      - "30022:22"
  # the following are hints on what volumes to mount if you want to persist data
  #  volumes:
  #    - data/gitlab/config:/etc/gitlab:rw
  #    - data/gitlab/logs:/var/log/gitlab:rw
  #    - data/gitlab/data:/var/opt/gitlab:rw

  postgresql:
    restart: always
    image: postgres:9.6.2-alpine
    environment:
      - POSTGRES_USER=gitlab
      - POSTGRES_PASSWORD=gitlab
      - POSTGRES_DB=gitlabhq_production
  # the following are hints on what volumes to mount if you want to persist data
  #  volumes:
  #    - data/postgresql:/var/lib/postgresql:rw

  redis:
    restart: always
    image: redis:3.0.7-alpine

What I want is gitlab to be accessible through gitlab.mydomain.com.

Have I forgotten anything in the config? Or do I need to add the routing part inside Apache/Nginx?

Never mind, got it working by adding an A-record in my domain config, and adding a server block inside the nginx configuration.