golang-patterns

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:

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

// 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:

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

func workerPool(jobs <-chan Job, results chan<- Result, workers int) {
    var wg sync.WaitGroup
    for i := 0; i < workers; i++ {
        wg.Add(1)
        go func() {
            defer wg.Done()
            for job := range jobs {
                results <- processJob(job)
            }
        }()
    }
    wg.Wait()
    close(results)
}

Context Propagation

Always pass context as first parameter:

func FetchUser(ctx context.Context, id string) (*User, error) {
    // Check context cancellation
    select {
    case <-ctx.Done():
        return nil, ctx.Err()
    default:
    }
    // ... fetch logic
}