Add gofmt output to CI test before calling test -z

We use a call to test -z together with go fmt because it doesn't output
a non-zero exit status (triggering CI test failure). However, we lose
useful debugging output from the go fmt call because test -z swallows
it. This adds very verbose formatting output to the CI test.

.gitlab-ci.yml

@@ -60,6 +60,7 @@ variables:
         lbzip2
 
 .go-test: &go-test
+  - gofmt -d .
   - test -z "$(go fmt ./...)"
   - go vet ./...
   - go test -v -race ./...