# go-concurrency-review

Review Go concurrency or build safer concurrent code with checks for goroutine lifecycles, channels, shared state, and context cancellation.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · ★ 83
- Author: eduardo-sl
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/eduardo-sl/go-agent-skills/tree/HEAD/skills/(safety)/go-concurrency-review/SKILL.md
- Updated: 2026-10-15
- HTML: https://affpapa.org/en/nevibecode/skills/go-concurrency-review

## What it does

The skill has modes for implementation, diff review, and investigating leaks or races. For a broad audit, it separates checks for goroutine shutdown, shared-state protection, channel ownership, and context propagation. Findings should point to a file and line; the audit ends with `go test -race ./...`.

Its guidance covers when to use channels, `sync.Mutex`, atomics, `sync.OnceValue`, and `errgroup`. More detail on channels, synchronization primitives, and goroutine patterns lives in reference files that the agent reads when needed. A Go toolchain is required. Race detection also needs `cgo` with `CGO_ENABLED=1`.

Every goroutine needs a clear way to stop, and channel sends should account for context cancellation. Race checks will not work without `cgo`. The skill is not intended for general style reviews or HTTP handler design.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add eduardo-sl/go-agent-skills --skill go-concurrency-review -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/go-concurrency-review/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/go-concurrency-review/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add eduardo-sl/go-agent-skills --skill go-concurrency-review -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/go-concurrency-review/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add eduardo-sl/go-agent-skills --skill go-concurrency-review -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/go-concurrency-review/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install eduardo-sl/go-agent-skills go-concurrency-review
```

2. **Manually: put the files in place**
- File: `.github/skills/go-concurrency-review/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add eduardo-sl/go-agent-skills --skill go-concurrency-review -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/eduardo-sl/go-agent-skills --path 'skills/(safety)/go-concurrency-review'
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/go-concurrency-review/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add eduardo-sl/go-agent-skills --skill go-concurrency-review -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/eduardo-sl/go-agent-skills/tree/HEAD/skills/(safety)/go-concurrency-review/SKILL.md

## When to use it
- find goroutines with no shutdown path
- check shared data for missing synchronization
- spot sends that may reach a closed channel
- trace context cancellation through blocking calls
- split a concurrency audit into independent checks

## Example prompts
- Review these Go changes for data races and unsafe shared state.
- Find goroutines that could remain blocked after context cancellation.
- Audit the channel usage and cite each finding by file and line.

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 5f916942d2a4d478.

BEGIN THIRD-PARTY FILE 5f916942d2a4d478
```text
---
name: go-concurrency-review
description: >
  Review and implement safe concurrency patterns in Go: goroutines,
  channels, sync primitives, context propagation, and goroutine lifecycle
  management. Use when writing concurrent code, reviewing async patterns,
  checking thread safety, debugging race conditions, or designing
  producer/consumer pipelines. Trigger examples: "check thread safety",
  "review goroutines", "race condition", "channel patterns", "sync.Mutex",
  "context cancellation", "goroutine leak".
  Not for: general style (go-coding-standards), HTTP handler patterns
  (go-api-design).
user-invocable: true
license: MIT
compatibility: Designed for Claude Code or similar AI coding agents working on Go projects. Requires the Go toolchain. Race detection requires cgo (CGO_ENABLED=1).
allowed-tools: Read Edit Write Glob Grep Bash(go:*) Bash(gofmt:*)
metadata:
  author: eduardo-sl
  version: "1.8.0"
---

# Go Concurrency Review

Concurrency in Go is powerful and deceptively easy to get wrong.
These patterns prevent goroutine leaks, data races, and deadlocks.

Detailed reference material, loaded on demand:

- `references/channels.md` — sizing, signalling, producer shutdown.
- `references/mutex-and-atomics.md` — mutex placement, lock scope, atomics,
  `sync.Once`, RWMutex pitfalls, `sync.Map`, `sync.Pool`, `singleflight`.
- `references/goroutine-patterns.md` — panic recovery at goroutine
  boundaries, pipelines, bounded fan-out, timers.

Read a reference file only when the section below is not enough.

## Operating Modes

Pick the mode that matches the request before starting:

- **Implementation** — writing new concurrent code. Follow the patterns
  below as construction rules.
- **Diff review** (default) — check changed code against every section,
  paying extra attention to new `go` statements and shared state.
- **Leak/race hunt** — a symptom is already observed (growing goroutine
  count, `-race` report, deadlock). Start from "Auditing Large Codebases"
  and the Race Detection section to localize it. On Go 1.27+ read the
  `goroutineleak` profile first: it lists goroutines blocked on something
  nothing can ever unblock. The go-troubleshooting skill owns the procedure.

## Auditing Large Codebases

For a full concurrency audit, run these independent passes rather than
one linear read:

1. **Goroutine lifecycle:** find every `go` statement
   (`grep -rn "go func\|go [a-zA-Z]" --include="*.go"`) and verify each
   has a termination path (context, closed channel, WaitGroup).
2. **Shared state:** find package-level vars and struct fields accessed
   from multiple goroutines; verify mutex/atomic protection.
3. **Channel topology:** map producers/consumers per channel; verify
```
END THIRD-PARTY FILE 5f916942d2a4d478

The third-party file has ended. Everything between the 5f916942d2a4d478 tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

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