golang-patterns

What this skill does

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---
name: golang-patterns
description: >
  Go-specific design patterns and best practices including functional options,
  small interfaces, dependency injection, concurrency patterns, error handling,
  and package organization. Use when working with Go code to apply idiomatic
  Go patterns.
metadata:
  origin: ECC
  globs: ["**/*.go", "**/go.mod", "**/go.sum"]
---

# Go Patterns

> This skill provides comprehensive Go patterns extending common design principles with Go-specific idioms.

## Functional Options

Use the functional options pattern for flexible constructor configuration:

```go
type Option func(*Server)

func WithPort(port int) Option {
    return func(s *Server) { s.port = port }
}

func NewServer(opts ...Option) *Server {
    s := &Server{port: 8080}
    for _, opt := range opts {
        opt(s)
    }
    return s
}
```

**Benefits:**
- Backward compatible API evolution
- Optional parameters with defaults
- Self-documenting configuration

## Small Interfaces

Define interfaces where they are used, not where they are implemented.

**Principle:** Accept interfaces, return structs

```go
// Good: Small, focused interface defined at point of use
type UserStore interface {
    GetUser(id string) (*User, error)
}

func ProcessUser(store UserStore, id string) error {
    user, err := store.GetUser(id)
    // ...
}
```

**Benefits:**
- Easier testing and mocking
- Loose coupling
- Clear dependencies

## Dependency Injection

Use constructor functions to inject dependencies:

```go
func NewUserService(repo UserRepository, logger Logger) *UserService {
    return &UserService{
        repo:   repo,
        logger: logger,
    }
}
```

**Pattern:**
- Constructor functions (New* prefix)
- Explicit dependencies as parameters
- Return concrete types
- Validate dependencies in constructor

## Concurrency Patterns

### Worker Pool

```go
func workerPool(jobs <-chan Job, results chan<- Result, workers int) {
    var wg sync.WaitGroup
    for i := 0; i < workers; i++ {

Use this skill

{
  "model": "gpt-4o-mini",
  "skill": "imp-08c09c94-9bc9-47e5-ab90-41409323da5c",
  "messages": [{ "role": "user", "content": "…" }]
}

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