Idiomatic Go patterns and best practices for building robust, efficient, and maintainable applications.
When to Activate
- Writing new Go code
- Reviewing Go code
- Refactoring existing Go code
- Designing Go packages/modules
Core Principles
1. Simplicity and Clarity
Go favors simplicity over cleverness. Code should be obvious and easy to read.
func GetUser(id string) (*User, error) {
user, err := db.FindUser(id)
if err != nil {
return nil, fmt.Errorf("get user %s: %w", id, err)
}
return user, nil
}
2. Make the Zero Value Useful
// Good: Zero value is useful
type Counter struct {
mu sync.Mutex
count int // zero value is 0, ready to use
}
func (c *Counter) Inc() {
c.mu.Lock()
c.count++
c.mu.Unlock()
}
// Good: bytes.Buffer works with zero value
var buf bytes.Buffer
buf.WriteString("hello")
3. Accept Interfaces, Return Structs
// Good: Accepts interface, returns concrete type
func ProcessData(r io.Reader) (*Result, error) {
data, err := io.ReadAll(r)
if err != nil {
return nil, err
}
return &Result{Data: data}, nil
}
Error Handling Patterns
Error Wrapping with Context
func LoadConfig(path string) (*Config, error) {
data, err := os.ReadFile(path)
if err != nil {
return nil, fmt.Errorf("load config %s: %w", path, err)
}
var cfg Config
if err := json.Unmarshal(data, &cfg); err != nil {
return nil, fmt.Errorf("parse config %s: %w", path, err)
}
return &cfg, nil
}
Custom Error Types
// Define domain-specific errors
type ValidationError struct {
Field string
Message string
}
func (e *ValidationError) Error() string {
return fmt.Sprintf("validation failed on %s: %s", e.Field, e.Message)
}
// Sentinel errors for common cases
var (
ErrNotFound = errors.New("resource not found")
ErrUnauthorized = errors.New("unauthorized")
ErrInvalidInput = errors.New("invalid input")
)
Concurrency Patterns
Worker Pool
func WorkerPool(jobs <-chan Job, results chan<- Result, numWorkers int) {
var wg sync.WaitGroup
for i := 0; i < numWorkers; i++ {
wg.Add(1)
go func() {
defer wg.Done()
for job := range jobs {
results <- process(job)
}
}()
}
wg.Wait()
close(results)
}
Context for Cancellation and Timeouts
func FetchWithTimeout(ctx context.Context, url string) ([]byte, error) {
ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
defer cancel()
req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
if err != nil {
return nil, fmt.Errorf("create request: %w", err)
}
resp, err := http.DefaultClient.Do(req)
if err != nil {
return nil, fmt.Errorf("fetch %s: %w", url, err)
}
defer resp.Body.Close()
return io.ReadAll(resp.Body)
}
Graceful Shutdown
func GracefulShutdown(server *http.Server) {
quit := make(chan os.Signal, 1)
signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
<-quit
log.Println("Shutting down server...")
ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
defer cancel()
if err := server.Shutdown(ctx); err != nil {
log.Fatalf("Server forced to shutdown: %v", err)
}
log.Println("Server exited")
}
Interface Design
Small, Focused Interfaces
// Good: Single-method interfaces
type Reader interface {
Read(p []byte) (n int, err error)
}
type Writer interface {
Write(p []byte) (n int, err error)
}
type Closer interface {
Close() error
}
// Compose interfaces as needed
type ReadWriteCloser interface {
Reader
Writer
Closer
}
Quick Reference: Go Idioms
| Idiom | Description |
|---|
| Accept interfaces, return structs | Functions accept interface params, return concrete types |
| Errors are values | Treat errors as first-class values, not exceptions |
| Don’t communicate by sharing memory | Use channels for coordination between goroutines |
| Make the zero value useful | Types should work without explicit initialization |
| Clear is better than clever | Prioritize readability over cleverness |
| Return early | Handle errors first, keep happy path unindented |
Go code should be boring in the best way - predictable, consistent, and easy to understand. When in doubt, keep it simple.