chore(ci): add coverage reporting

.gitlab-ci.yml

@@ -14,6 +14,13 @@ coverage:
     stage: cover
     image: alpinelinux/golang
     script:
-        - go test $(go list ./... | grep -v /vendor/) -covermode=atomic -coverprofile .testCoverage.txt
+        - go get github.com/boumenot/gocover-cobertura
+        - go test -coverprofile=coverage.txt -covermode=count ./...
+        - gocover-cobertura < coverage.txt > coverage.xml
     tags:
         - docker-alpine
+    artifacts:
+      name: ${CI_JOB_NAME}-${CI_COMMIT_REF_NAME}-${CI_COMMIT_SHA}
+      expire_in: 2 days
+      reports:
+        cobertura: coverage.xml