Add basic go test coverage to PRs

 - Building on the prior CI changes to lint and produce test artifacts,
   use the action go-coverage-report to examine the cover.out file
   produced to generate a small coverage report

.github/workflows/test.yaml

@@ -39,3 +39,15 @@ jobs:
         path: test/*.xml
         reporter: java-junit
         output-to: 'step-summary'
+
+  coverage:
+    name: code coverage
+    if: github.event_name == 'pull_request' # Do not run when workflow is triggered by push to main branch
+    runs-on: ubuntu-latest
+    needs: test # Depends on the artifact uploaded by the "test" job
+    steps:
+    - uses: fgrosse/go-coverage-report@v1.0.1
+      with:
+        coverage-artifact-name: "test-results" # can be omitted if you used this default value
+        coverage-file-name: "cover.out"
+      continue-on-error: true