Go Change

---
name: go-change
description: Checklist for writing idiomatic, safe, stdlib-only Go under go/ with tests and the local toolchain. Use when a task's spec names Go, touches go/, or adds a Go test, fuzz target or parser.
---

# Go change

Policy: docs/adr/0001-language-policy.md. Toolchain setup: docs/go-toolchain.md. Go files live under `go/`.

Follow these steps in order.

1. Check the toolchain: `export PATH=~/.local/go/bin:$PATH GOTOOLCHAIN=local; go version`. If `go` is missing, stop and report to your lead (you do not install toolchains).
2. Read the neighbouring Go code and match its package layout, naming and error style.
3. Write the code. Rules:
   - Errors are always checked and wrapped with `%w` (`fmt.Errorf("read %s: %w", p, err)`); never discard one with `_ =`.
   - No `panic` on input. Guards fail closed: `recover` in `main` -> exit 2.
   - `exec.Command` takes an argv slice only. Never `sh -c` with a built string.
   - No `unsafe`, no cgo, no reflect on input.
   - Stdlib only: no `require` in `go/go.mod` without an owner decision. If you need one, stop and report to your lead.
   - No binaries in git (build output stays gitignored).
4. Write tests: table tests for new logic, a fuzz target (`func FuzzX(f *testing.F)`) for every parser.
5. From `go/` run, and fix until clean: `gofmt -l .` (empty output), `go vet ./...`, `go test -race -count=1 ./...`.
6. A port of existing Python behaviour needs a differential test against the old implementation: zero loosened and zero tightened cases. RE2 has no lookaround and its `\w \b \d \s` are ASCII-only; use explicit Unicode classes or a hand matcher and test non-ASCII input.
7. Put the three commands and their output in the PR body; CI job `go` must be green before in_review.

Stop and report to your lead when: `go` is missing, a dependency is needed, or the spec does not name Go but asks for a parser or daemon.