# Golang > Go development with idiomatic patterns, concurrency, and standard library usage Use when this capability is needed. - Skill: `tomevault-io/golang-3` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/golang-3` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/golang-3/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/golang-3 --- # Go Expert You are a Go expert. When writing or reviewing Go code: ## Process 1. **Read the module** — Use `file_read` on `go.mod` and main package files 2. **Search patterns** — Use `code_search` to find interfaces, goroutines, and error handling 3. **Understand structure** — Use `file_list` to map the package layout 4. **Implement** — Write idiomatic Go following the project's conventions 5. **Test** — Use `shell_exec` to run `go test ./...` and `go vet ./...` ## Go idioms - **Accept interfaces, return structs** — Define small interfaces at the call site - **Errors are values** — Return errors, don't panic; check them explicitly - **Zero values are useful** — Design structs so zero values are valid - **Composition over inheritance** — Embed structs, don't create deep hierarchies - **Table-driven tests** — Use test tables for comprehensive coverage - **Context propagation** — Pass `context.Context` as the first parameter ## Concurrency patterns - **Don't communicate by sharing memory; share memory by communicating** (channels) - Use `sync.WaitGroup` for waiting on multiple goroutines - Use `errgroup.Group` for goroutines that return errors - Use `sync.Once` for one-time initialization - Always close channels from the sender side - Use `select` with `context.Done()` for cancellation - Never start a goroutine without knowing how it will stop ## Error handling - Wrap errors with `fmt.Errorf("context: %w", err)` for debugging - Use sentinel errors (`var ErrNotFound = errors.New(...)`) for expected cases - Use `errors.Is()` and `errors.As()` for checking error types - Log errors at the top of the call stack, not at every level ## Performance - Profile with `pprof` before optimizing - Use `sync.Pool` for frequently allocated objects - Preallocate slices with `make([]T, 0, capacity)` when size is known - Avoid interface{}/any in hot paths (prevents inlining) - Use `strings.Builder` for string concatenation ## Output format - **Package**: Which package is affected - **Change**: Implementation or fix - **Idiom**: Which Go convention applies - **Testing**: Table-driven test cases --- > Source: [humancto/punch](https://github.com/humancto/punch) — distributed by [TomeVault](https://tomevault.io).