Add a separate test stage

Allows Gitlab to gather MR metrics on test coverage and other
issues. Tests are anyway run again by dpkg-build.

.gitlab-ci.yml

@@ -2,3 +2,14 @@ include:
   - "https://git.autistici.org/ai3/build-deb/raw/master/ci-backports.yml"
   - "https://git.autistici.org/ai3/build-container/raw/master/common.yml"
 
+test:
+  stage: test
+  image: registry.git.autistici.org/ai3/docker/test/golang:master
+  script:
+    - run-go-test ./...
+  artifacts:
+    when: always
+    reports:
+      cobertura: cover.xml
+      junit: report.xml
+