Go to your profile in GitLab (Edit Profile) click on Access Tokens and create a token there with sufficient privileges.
docker build -t gitlab-backups .
docker run \
-it \
-e GITLAB_TOKEN="YOUR_SUPER_SECRET_TOKEN_GOES_HERE" \
-e GITLAB_HOST="https://LookMa.imma.git.host.example.com" \
-v $(pwd)/data:/data \
gitlab-backups