/go-concurrency-patterns

name: go-concurrency-patterns
description: Master Go concurrency with goroutines, channels, sync primitives, and context. Use when building concurrent Go applications, implementing worker pools, or debugging race conditions.

Go Concurrency Patterns

Production patterns for Go concurrency including goroutines, channels, synchronization primitives, and context management.

When to Use This Skill

• Building concurrent Go applications
• Implementing worker pools and pipelines
• Managing goroutine lifecycles
• Using channels for communication
• Debugging race conditions
• Implementing graceful shutdown

Core Concepts

1. Go Concurrency Primitives

| Primitive | Purpose | | ----------------- | -------------------------------- | | `goroutine` | Lightweight concurrent execution | | `channel` | Communication between goroutines | | `select` | Multiplex channel operations | | `sync.Mutex` | Mutual exclusion | | `sync.WaitGroup` | Wait for goroutines to complete | | `context.Context` | Cancellation and deadlines |

2. Go Concurrency Mantra

Don't communicate by sharing memory;
share memory by communicating.

Quick Start

package main

import (
    "context"
    "fmt"
    "sync"
    "time"
)

func main() {
    ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
    defer cancel()

    results := make(chan string, 10)
    var wg sync.WaitGroup

    // Spawn workers
    for i := 0; i < 3; i++ {
        wg.Add(1)
        go worker(ctx, i, results, &wg)
    }

    // Close results when done
    go func() {
        wg.Wait()
        close(results)
    }()

    // Collect results
    for result := range results {
        fmt.Println(result)
    }
}

func worker(ctx context.Context, id int, results chan<- string, wg *sync.WaitGroup) {
    defer wg.Done()

    select {
    case <-ctx.Done():
        return
    case results <- fmt.Sprintf("Worker %d done", id):
    }
}

Detailed patterns and worked examples

Detailed pattern documentation lives in `references/details.md`. Read that file when the navigation tier above is insufficient.

Best Practices

Do's

• **Use context** - For cancellation and deadlines
• **Close channels** - From sender side only
• **Use errgroup** - For concurrent operations with errors
• **Buffer channels** - When you know the count
• **Prefer channels** - Over mutexes when possible

Don'ts

• **Don't leak goroutines** - Always have exit path
• **Don't close from receiver** - Causes panic
• **Don't use shared memory** - Unless necessary
• **Don't ignore context cancellation** - Check ctx.Done()
• **Don't use time.Sleep for sync** - Use proper primitives