golang-lint

---
name: golang-lint
description: "Provides linting best practices and golangci-lint configuration for Go projects. Covers running linters, configuring .golangci.yml, suppressing warnings with nolint directives, interpreting lint output, and managing linter settings. Use this skill whenever the user runs linters, configures golangci-lint, asks about lint warnings or suppressions, sets up code quality tooling, or asks which linters to enable for a Go project. Also use when the user mentions golangci-lint, go vet, staticcheck, revive, or any Go linting tool."
user-invocable: true
license: MIT
compatibility: Designed for Claude Code or similar AI coding agents, and for projects using Golang.
metadata:
  author: samber
  version: "1.1.1"
  openclaw:
    emoji: "🧹"
    homepage: https://github.com/samber/cc-skills-golang
    requires:
      bins:
        - go
        - golangci-lint
    install:
      - kind: brew
        formula: golangci-lint
        bins: [golangci-lint]
allowed-tools: Read Edit Write Glob Grep Bash(go:*) Bash(golangci-lint:*) Bash(git:*) Agent
---

**Persona:** You are a Go code quality engineer. You treat linting as a first-class part of the development workflow — not a post-hoc cleanup step.

**Modes:**

- **Setup mode** — configuring `.golangci.yml`, choosing linters, enabling CI: follow the configuration and workflow sections sequentially.
- **Coding mode** — writing new Go code: launch a background agent running `golangci-lint run --fix` on the modified files only while the main agent continues implementing the feature; surface results when it completes.
- **Interpret/fix mode** — reading lint output, suppressing warnings, fixing issues on existing code: start from "Interpreting Output" and "Suppressing Lint Warnings"; use parallel sub-agents for large-scale legacy cleanup.

# Go Linting

## Overview

`golangci-lint` is the standard Go linting tool. It aggregates 100+ linters into a single binary, runs them in parallel, and provides a unified configuration format. Run it frequently during development and always in CI.

Every Go project MUST have a `.golangci.yml` — it is the **source of truth** for which linters are enabled and how they are configured. See the [recommended configuration](./assets/.golangci.yml) for a production-ready setup with 33 linters enabled.

## Quick Reference

```bash
# Run all configured linters
golangci-lint run ./...

# Auto-fix issues where possible
golangci-lint run --fix ./...

# Format code (golangci-lint v2+)
golangci-lint fmt ./...

# Run a single linter only
golangci-lint run --enable-only govet ./...

# List all available linters
golangci-lint linters

# Verbose output with timing info
golangci-lint run --verbose ./...
```

## Configuration

The [recommended .golangci.yml](./assets/.golangci.yml) provides a production-ready setup with 33 linters. For configuration details, linter categories, and per-linter descriptions, see the **[linter reference](./references/linter-reference.md)** — which linters check for what (correctness, style, complexity, performance, security), descriptions of all 33+ linters, and when each one is useful.

## Suppressing Lint Warnings

Use `//nolint` directives sparingly — fix the root cause first.

```go
// Good: specific linter + justification
//nolint:errcheck // fire-and-forget logging, error is not actionable
_ = logger.Sync()

// Bad: blanket suppression without reason
//nolint
_ = logger.Sync()
```

Rules:

1. **//nolint directives MUST specify the linter name**: `//nolint:errcheck` not `//nolint`
2. **//nolint directives MUST include a justification comment**: `//nolint:errcheck // reason`
3. **The `nolintlint` linter enforces both rules above** — it flags bare `//nolint` and missing reasons
4. **NEVER suppress security linters** (bodyclose, sqlclosecheck) without a very strong reason

For comprehensive patterns and examples, see **[nolint directives](./references/nolint-directives.md)** — when to suppress, how to write justifications, patterns for per-line vs per-function suppression, and anti-patterns.

## Development Workflow

1. **Linters SHOULD be run after every significant change**: `golangci-lint run ./...`
2. **Auto-fix what you can**: `golangci-lint run --fix ./...`
3. **Format before committing**: `golangci-lint fmt ./...`
4. **Incremental adoption on legacy code**: set `issues.new-from-rev` in `.golangci.yml` to only lint new/changed code, then gradually clean up old code

Makefile targets (recommended):

```makefile
lint:
	golangci-lint run ./...

lint-fix:
	golangci-lint run --fix ./...

fmt:
	golangci-lint fmt ./...
```

For CI pipeline setup (GitHub Actions with `golangci-lint-action`), see the `samber/cc-skills-golang@golang-continuous-integration` skill.

## Interpreting Output

Each issue follows this format:

```
path/to/file.go:42:10: message describing the issue (linter-name)
```

The linter name in parentheses tells you which linter flagged it. Use this to:

- Look up the linter in the [reference](./references/linter-reference.md) to understand what it checks
- Suppress with `//nolint:linter-name // reason` if it's a false positive
- Use `golangci-lint run --verbose` for additional context and timing

## Common Issues

| Problem | Solution |
| --- | --- |
| "deadline exceeded" | Increase `run.timeout` in `.golangci.yml` (default: 5m) |
| Too many issues on legacy code | Set `issues.new-from-rev: HEAD~1` to lint only new code |
| Linter not found | Check `golangci-lint linters` — linter may need a newer version |
| Conflicts between linters | Disable the less useful one with a comment explaining why |
| v1 config errors after upgrade | Run `golangci-lint migrate` to convert config format |
| Slow on large repos | Reduce `run.concurrency` or exclude directories in `run.skip-dirs` |

## Parallelizing Legacy Codebase Cleanup

When adopting linting on a legacy codebase, use up to 5 parallel sub-agents (via the Agent tool) to fix independent linter categories simultaneously:

- Sub-agent 1: Run `golangci-lint run --fix ./...` for auto-fixable issues
- Sub-agent 2: Fix security linter findings (bodyclose, sqlclosecheck, gosec)
- Sub-agent 3: Fix error handling issues (errcheck, nilerr, wrapcheck)
- Sub-agent 4: Fix style and formatting (gofumpt, goimports, revive)
- Sub-agent 5: Fix code quality (gocritic, unused, ineffassign)

## Cross-References

- → See `samber/cc-skills-golang@golang-continuous-integration` skill for CI pipeline with golangci-lint-action
- → See `samber/cc-skills-golang@golang-code-style` skill for style rules that linters enforce
- → See `samber/cc-skills-golang@golang-security` skill for SAST tools beyond linting (gosec, govulncheck)