# Golang > Use when the project uses Go for systems programming or backend services - Skill: `tomevault-io/golang-5` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/golang-5` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/golang-5/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-5 --- # Go Best Practices ## Error Handling Check every error. The `if err != nil` pattern is intentional -- Go makes error handling explicit. Never discard errors with `_`. Wrap errors with context using `fmt.Errorf("doing X: %w", err)` so call chains produce readable messages. Use sentinel errors (`var ErrNotFound = errors.New("not found")`) for expected conditions that callers check with `errors.Is()`. Use custom error types for errors that carry structured data. ## Project Structure Follow the standard layout: `cmd/` for application entry points, `internal/` for private packages, `pkg/` for public libraries (if any). Keep `main.go` minimal -- it wires up dependencies and starts the server. One package per directory. Package names should be short, lowercase, and descriptive. Avoid `util` or `common` packages -- they become dumping grounds. ## Concurrency Do not communicate by sharing memory -- share memory by communicating. Use channels for synchronization between goroutines. Use `sync.Mutex` only for protecting simple shared state where channels would be overkill. Always ensure goroutines can be stopped. Pass `context.Context` and check `ctx.Done()`. Leaking goroutines is a memory leak that grows over time. Use `sync.WaitGroup` when you need to wait for a known number of goroutines to complete. Use `errgroup.Group` when any goroutine failure should cancel the rest. ## Interfaces Define interfaces where they are used, not where they are implemented. Keep interfaces small -- one or two methods is ideal. The `io.Reader` and `io.Writer` interfaces are the gold standard. Accept interfaces, return structs. This makes code testable -- callers can inject mocks that satisfy the interface. ## Testing Use table-driven tests for functions with multiple input/output combinations. Name test cases clearly. Use `t.Run()` for subtests so failures identify which case broke. Use `testing.T.Helper()` in test helper functions so failure messages point to the calling test, not the helper. ## Dependencies Use `go mod tidy` to keep `go.mod` clean. Vendor dependencies with `go mod vendor` for reproducible builds in CI. Avoid unnecessary dependencies -- the standard library is comprehensive. Check if `net/http`, `encoding/json`, or `os` already do what you need. ## Performance Profile before optimizing with `pprof`. Pre-allocate slices with `make([]T, 0, expectedCap)` when the size is known. Avoid string concatenation in loops -- use `strings.Builder`. Reduce allocations by reusing buffers with `sync.Pool` for hot paths. --- > Source: [calcosmic/Aether](https://github.com/calcosmic/Aether) — distributed by [TomeVault](https://tomevault.io).