docker 20 with dind for gitlab runner

.gitlab-ci.yaml

image: some-image

# dind is necessary for docker
services:
  - name: docker:20.10.10-dind
    alias: docker
    # THIS IS IMPORTANT!
    command: ["--tls=false"]

build:
  stage: build
  image: docker:20.10.10
  variables: 
    # THIS IS IMPORTANT!
    DOCKER_TLS_CERTDIR: "" 
  before_script:
    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY 
  script:
    - docker build .