rockcookies/golang-lint

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 for a production-ready setup with 48 linters enabled.

Quick Reference

# 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 provides a production-ready setup with 33 linters. For configuration details, linter categories, and per-linter descriptions, see the linter reference — 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.

// 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 (gosec, bodyclose, sqlclosecheck) without a very strong reason

For comprehensive patterns and examples, see nolint directives — 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):

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 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 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" | Set or increase run.timeout in .golangci.yml; golangci-lint v2 defaults to no timeout (0) | | 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 paths with linters.exclusions.paths / formatters.exclusions.paths |

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 golang-continuous-integration skill for CI pipeline with golangci-lint-action
• → See golang-code-style skill for style rules that linters enforce
• → See golang-security skill for SAST tools beyond linting (gosec, govulncheck)
• → See golang-continuous-integration skill for automated AI-driven code review in CI using these guidelines