ci: cache go dependencies for tests

.gitlab-ci.yml

@@ -8,11 +8,18 @@ stages:
 test:
   stage: test
   image: golang:alpine
+  variables:
+    GOPATH: $CI_PROJECT_DIR/.go
+  before_script:
+    - mkdir -p .go
   script:
     - go mod download
     - go test ./... -v -coverprofile=coverage.txt -covermode count
     - go get github.com/boumenot/gocover-cobertura
     - go run github.com/boumenot/gocover-cobertura < coverage.txt > coverage.xml
+  cache:
+    paths:
+      - .go/pkg/mod/
   artifacts:
     reports:
       coverage_report: