Enable gitlab ci cache for go deps

.gitlab-ci.yml

@@ -11,5 +11,10 @@ compile:
   artifacts:
     paths:
       - hepto
-
-
+  variables:
+    GOPATH: $CI_PROJECT_DIR/.go
+  before_script:
+    - mkdir -p .go
+  cachew:
+    paths:
+      - .go/pkg/mod/