Verifying BuildKit Cache Effectiveness

Systematically verify—from CI logs only—that Docker RUN --mount=type=cache (Go GOMODCACHE and GOCACHE) is:

1. Persisted across jobs
2. Restored by GitHub Actions
3. Injected back into BuildKit
4. Actually speeding up go build

Prerequisites

This checklist assumes:

• Dockerfile uses BuildKit cache mounts:
  • RUN --mount=type=cache,target=/go/pkg/mod (GOMODCACHE)
  • RUN --mount=type=cache,target=/root/.cache/go-build (GOCACHE)
• GitHub Actions workflow:
  • Uses actions/cache@v5 to persist a host directory (CACHE_DIR, e.g. cache-mount/)