go-concurrency

# Go Concurrency Skill

This skill provides expert guidance on Go's concurrency primitives and patterns, covering goroutines, channels, synchronization, and best practices for building concurrent systems.

## When to Use

Activate this skill when:
- Implementing concurrent/parallel processing
- Working with goroutines and channels
- Using synchronization primitives (mutexes, wait groups, etc.)
- Debugging race conditions
- Optimizing concurrent performance
- Implementing worker pools or pipelines
- Handling context cancellation

## Goroutine Fundamentals

### Basic Goroutines

```go
// Simple goroutine
go func() {
    fmt.Println("Hello from goroutine")
}()

// Goroutine with parameters
go func(msg string) {
    fmt.Println(msg)
}("Hello")

// Goroutine with closure
message := "Hello"
go func() {
    fmt.Println(message) // Captures message
}()
```

### Common Pitfalls

```go
// ❌ BAD: Loop variable capture
for i := 0; i < 5; i++ {
    go func() {
        fmt.Println(i) // All goroutines may print 5
    }()
}

// ✅ GOOD: Pass as parameter
for i := 0; i < 5; i++ {
    go func(n int) {
        fmt.Println(n) // Each prints correct value
    }(i)
}

// ✅ GOOD: Create local copy
for i := 0; i < 5; i++ {
    i := i // Create new variable
    go func() {
        fmt.Println(i)
    }()
}
```

## Channel Patterns

### Channel Types

```go
// Unbuffered channel (synchronous)
ch := make(chan int)

// Buffered channel (asynchronous up to buffer size)
ch := make(chan int, 10)

// Send-only channel
func send(ch chan<- int) {
    ch <- 42
}

// Receive-only channel
func receive(ch <-chan int) {
    value := <-ch
}

// Bidirectional channel
ch := make(chan int)
```

### Channel Operations

```go
// Send
ch <- value

// Receive
value := <-ch

// Receive with ok check
value, ok := <-ch
if !ok {
    // Channel closed
}

// Close channel
close(ch)

// Range over channel
for value := range ch {
    fmt.Println(value)
}
```

### Select Statement

```go
// Wait for first available operat