Add go cache

.gitlab/_common.gitlab-ci.yml

@@ -12,3 +12,13 @@ image: docker:$DOCKER_VERSION-git
 .login_registry:
   before_script:
     - docker login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD $CI_REGISTRY
+
+.go-cache:
+  variables:
+    GOPATH: $CI_PROJECT_DIR/.go
+  before_script:
+    - mkdir -p .go
+    - export PATH=$PATH:$GOROOT/bin:$GOPATH/bin
+  cache:
+    paths:
+      - .go/pkg/mod/