Update .gitlab-ci.yml file

.gitlab-ci.yml

@@ -18,11 +18,14 @@ variables:
   DOCKER_HOST: tcp://docker:2375
   DOCKER_DRIVER: overlay2
   DOCKER_TLS_CERTDIR: ""
+  DOCKER_HOST: "unix:///var/run/docker.sock"
 
 build-docker-image:
   image: docker:latest
   stage: build
   services:
+    - docker:dind
+  variables:
     - name: docker:dind
       command: ["--tls=false"]
   before_script: