go clean — Hands-on Tasks¶

Go 1.21+. Each task has explicit acceptance criteria.

Task 1: Preview before cleaning¶

Use -n to see what would happen.

Acceptance criteria - [ ] go clean -n -cache prints the would-be removal of $GOCACHE without removing it. - [ ] go clean -n -modcache does the same for the module cache. - [ ] You confirm the caches still exist afterward.

Task 2: Expire the test cache¶

Force tests to re-run.

Acceptance criteria - [ ] go test ./... shows (cached) on a second run. - [ ] go clean -testcache then go test ./... re-runs everything (no (cached)). - [ ] You contrast this with go test -count=1.

Task 3: Find the cache locations¶

Locate and size the caches.

Acceptance criteria - [ ] go env GOCACHE and go env GOMODCACHE print their paths. - [ ] You measure their sizes (du -sh). - [ ] You explain which one usually holds the most data.

Task 4: Reclaim module cache disk¶

Wipe and re-warm the module cache.

Acceptance criteria - [ ] go clean -modcache removes the module cache (no permission errors). - [ ] go mod download re-populates it. - [ ] go mod verify reports all modules verified.

Task 5: Cold-cache build¶

Verify a build from a cold cache.

Acceptance criteria - [ ] go clean -cache empties the build cache. - [ ] go build ./... rebuilds everything (slow first run). - [ ] An immediate second build is fast again (cache re-warmed).

Task 6: Clean installed artifacts¶

Remove an installed binary.

Acceptance criteria - [ ] go install ./cmd/tool installs a binary. - [ ] go clean -i ./cmd/tool removes the installed artifact for that package. - [ ] You note there is no general go uninstall.

Task 7: Fuzz cache¶

Clear generated fuzz corpora.

Acceptance criteria - [ ] A fuzz target run (go test -fuzz=Fuzz -fuzztime=5s) generates corpus entries. - [ ] go clean -fuzzcache clears the generated cache. - [ ] You confirm testdata/fuzz seed corpora are untouched.

Task 8: Diagnose before cleaning (reflection)¶

Practice not reaching for clean first.

Acceptance criteria - [ ] Given a "broken build," you first check go env GOFLAGS GOOS GOARCH, go version, and go build -x. - [ ] You write 2–3 sentences on why a clean that "fixes" a build usually hides the real cause.