Add job to evaluate Go 1.22 loop behavior changes

Use Go 1.21 series "mirror" image to perform builds using the
`loopvar` compiler flag. This new workflow job will be ued to
identify loops that compile differently using the new loop
semantics introduced as a preview in Go 1.21 and enabled by
default with the release of Go 1.22.

This new workflow job is set to `continue-on-error` in order to
verify that it works as intended. Once it has been proven to
work as intended `continue-on-error` will be set to `false`
and any identified loop behavior changes will be considered
a real CI failure requiring resolution.

refs GH-145

.github/workflows/lint-and-build-using-ci-matrix.yml

@@ -184,6 +184,43 @@ jobs:
  - name: Run all tests
  run: go test -mod=vendor -v ./...
 
+ # https://github.com/atc0005/shared-project-resources/issues/145
+ evaluate_loopvar_scoping_changes:
+ needs: assert_pr_branch_is_ahead_of_primary_branch
+ name: Evaluate loopvar scoping changes
+ runs-on: ubuntu-latest
+ # Default: 360 minutes
+ timeout-minutes: 10
+ # Don't flag the whole workflow as failed if this job fails. Once this
+ # workflow job proves itself we can mark it as required.
+ continue-on-error: true
+ container:
+ image: "ghcr.io/atc0005/go-ci:go-ci-mirror-build-go1.21"
+
+ steps:
+ - name: Print go version
+ run: go version
+
+ - name: Check out code
+ uses: actions/checkout@v4.1.1
+
+ # Mark the current working directory as a safe directory in git to
+ # resolve "dubious ownership" complaints.
+ #
+ # https://docs.github.com/en/actions/learn-github-actions/variables#default-environment-variables
+ # https://confluence.atlassian.com/bbkb/git-command-returns-fatal-error-about-the-repository-being-owned-by-someone-else-1167744132.html
+ # https://github.com/actions/runner-images/issues/6775
+ # https://github.com/actions/checkout/issues/766
+ - name: Mark the current working directory as a safe directory in git
+ # run: git config --global --add safe.directory "$GITHUB_WORKSPACE"
+ run: git config --global --add safe.directory "${PWD}"
+
+ - name: Assert loopvar flag does not change loop compilation behavior
+ run: >-
+ ! go build -gcflags=all=-d=loopvar=2 $(go list -mod=vendor ./...) 2>&1
+ | grep -Ev 'vendor/|/usr'
+ | grep --quiet 'now per-iteration'
+
  build_code:
  needs: assert_pr_branch_is_ahead_of_primary_branch
  name: Build codebase