.github: run unit tests only once, with coverage

We've been running the unit tests twice, once with and once without
coverage. Run them only once, with coverage.

.github/workflows/tests.yml

@@ -40,11 +40,19 @@ jobs:
       - name: Install golangci-lint
         run: curl -sfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh| sh -s -- -b $(go env GOPATH)/bin v1.23.7
 
+      - name: Install goveralls
+        run: GO111MODULE=off go get github.com/mattn/goveralls
+
       - name: Run golangci-lint
         run: $(go env GOPATH)/bin/golangci-lint run
 
       - name: Run unit tests
-        run: go test -v ./...
+        run: go test -v -race -covermode atomic -coverprofile=profile.cov ./...
+
+      - name: Send coverage to coveralls.io
+        env:
+          COVERALLS_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: $(go env GOPATH)/bin/goveralls -coverprofile=profile.cov -service=github
 
   old_rpm_build:
     name: "📦 RPM (golang-github-osbuild-composer)"