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堅牢で効率的かつ保守可能なGoアプリケーションを構築するための慣用的なGoパターン、ベストプラクティス、規約。
| name | golang-patterns |
| description | 堅牢で効率的かつ保守可能なGoアプリケーションを構築するための慣用的なGoパターン、ベストプラクティス、規約。 |
堅牢で効率的かつ保守可能なアプリケーションを構築するための慣用的なGoパターンとベストプラクティス。
Goは巧妙さよりもシンプルさを好みます。コードは明白で読みやすいものであるべきです。
// Good: Clear and direct
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
}
// Bad: Overly clever
func GetUser(id string) (*User, error) {
return func() (*User, error) {
if u, e := db.FindUser(id); e == nil {
return u, nil
} else {
return nil, e
}
}()
}
型を設計する際、そのゼロ値が初期化なしですぐに使用できるようにします。
// 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")
// Bad: Requires initialization
type BadCounter struct {
counts map[string]int // nil map will panic
}
関数はインターフェースパラメータを受け取り、具体的な型を返すべきです。
// 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
}
// Bad: Returns interface (hides implementation details unnecessarily)
func ProcessData(r io.Reader) (io.Reader, error) {
// ...
}
// Good: Wrap errors 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
}
// 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")
)
func HandleError(err error) {
// Check for specific error
if errors.Is(err, sql.ErrNoRows) {
log.Println("No records found")
return
}
// Check for error type
var validationErr *ValidationError
if errors.As(err, &validationErr) {
log.Printf("Validation error on field %s: %s",
validationErr.Field, validationErr.Message)
return
}
// Unknown error
log.Printf("Unexpected error: %v", err)
}
// Bad: Ignoring error with blank identifier
result, _ := doSomething()
// Good: Handle or explicitly document why it's safe to ignore
result, err := doSomething()
if err != nil {
return err
}
// Acceptable: When error truly doesn't matter (rare)
_ = writer.Close() // Best-effort cleanup, error logged elsewhere
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)
}
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)
}
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")
}
import "golang.org/x/sync/errgroup"
func FetchAll(ctx context.Context, urls []string) ([][]byte, error) {
g, ctx := errgroup.WithContext(ctx)
results := make([][]byte, len(urls))
for i, url := range urls {
i, url := i, url // Capture loop variables
g.Go(func() error {
data, err := FetchWithTimeout(ctx, url)
if err != nil {
return err
}
results[i] = data
return nil
})
}
if err := g.Wait(); err != nil {
return nil, err
}
return results, nil
}
// Bad: Goroutine leak if context is cancelled
func leakyFetch(ctx context.Context, url string) <-chan []byte {
ch := make(chan []byte)
go func() {
data, _ := fetch(url)
ch <- data // Blocks forever if no receiver
}()
return ch
}
// Good: Properly handles cancellation
func safeFetch(ctx context.Context, url string) <-chan []byte {
ch := make(chan []byte, 1) // Buffered channel
go func() {
data, err := fetch(url)
if err != nil {
return
}
select {
case ch <- data:
case <-ctx.Done():
}
}()
return ch
}
// 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
}
// In the consumer package, not the provider
package service
// UserStore defines what this service needs
type UserStore interface {
GetUser(id string) (*User, error)
SaveUser(user *User) error
}
type Service struct {
store UserStore
}
// Concrete implementation can be in another package
// It doesn't need to know about this interface
type Flusher interface {
Flush() error
}
func WriteAndFlush(w io.Writer, data []byte) error {
if _, err := w.Write(data); err != nil {
return err
}
// Flush if supported
if f, ok := w.(Flusher); ok {
return f.Flush()
}
return nil
}
myproject/
├── cmd/
│ └── myapp/
│ └── main.go # エントリポイント
├── internal/
│ ├── handler/ # HTTP ハンドラー
│ ├── service/ # ビジネスロジック
│ ├── repository/ # データアクセス
│ └── config/ # 設定
├── pkg/
│ └── client/ # 公開 API クライアント
├── api/
│ └── v1/ # API 定義（proto、OpenAPI）
├── testdata/ # テストフィクスチャ
├── go.mod
├── go.sum
└── Makefile
// Good: Short, lowercase, no underscores
package http
package json
package user
// Bad: Verbose, mixed case, or redundant
package httpHandler
package json_parser
package userService // Redundant 'Service' suffix
// Bad: Global mutable state
var db *sql.DB
func init() {
db, _ = sql.Open("postgres", os.Getenv("DATABASE_URL"))
}
// Good: Dependency injection
type Server struct {
db *sql.DB
}
func NewServer(db *sql.DB) *Server {
return &Server{db: db}
}
type Server struct {
addr string
timeout time.Duration
logger *log.Logger
}
type Option func(*Server)
func WithTimeout(d time.Duration) Option {
return func(s *Server) {
s.timeout = d
}
}
func WithLogger(l *log.Logger) Option {
return func(s *Server) {
s.logger = l
}
}
func NewServer(addr string, opts ...Option) *Server {
s := &Server{
addr: addr,
timeout: 30 * time.Second, // default
logger: log.Default(), // default
}
for _, opt := range opts {
opt(s)
}
return s
}
// Usage
server := NewServer(":8080",
WithTimeout(60*time.Second),
WithLogger(customLogger),
)
type Logger struct {
prefix string
}
func (l *Logger) Log(msg string) {
fmt.Printf("[%s] %s\n", l.prefix, msg)
}
type Server struct {
*Logger // Embedding - Server gets Log method
addr string
}
func NewServer(addr string) *Server {
return &Server{
Logger: &Logger{prefix: "SERVER"},
addr: addr,
}
}
// Usage
s := NewServer(":8080")
s.Log("Starting...") // Calls embedded Logger.Log
// Bad: Grows slice multiple times
func processItems(items []Item) []Result {
var results []Result
for _, item := range items {
results = append(results, process(item))
}
return results
}
// Good: Single allocation
func processItems(items []Item) []Result {
results := make([]Result, 0, len(items))
for _, item := range items {
results = append(results, process(item))
}
return results
}
var bufferPool = sync.Pool{
New: func() interface{} {
return new(bytes.Buffer)
},
}
func ProcessRequest(data []byte) []byte {
buf := bufferPool.Get().(*bytes.Buffer)
defer func() {
buf.Reset()
bufferPool.Put(buf)
}()
buf.Write(data)
// Process...
return buf.Bytes()
}
// Bad: Creates many string allocations
func join(parts []string) string {
var result string
for _, p := range parts {
result += p + ","
}
return result
}
// Good: Single allocation with strings.Builder
func join(parts []string) string {
var sb strings.Builder
for i, p := range parts {
if i > 0 {
sb.WriteString(",")
}
sb.WriteString(p)
}
return sb.String()
}
// Best: Use standard library
func join(parts []string) string {
return strings.Join(parts, ",")
}
# Build and run
go build ./...
go run ./cmd/myapp
# Testing
go test ./...
go test -race ./...
go test -cover ./...
# Static analysis
go vet ./...
staticcheck ./...
golangci-lint run
# Module management
go mod tidy
go mod verify
# Formatting
gofmt -w .
goimports -w .
linters:
enable:
- errcheck
- gosimple
- govet
- ineffassign
- staticcheck
- unused
- gofmt
- goimports
- misspell
- unconvert
- unparam
linters-settings:
errcheck:
check-type-assertions: true
govet:
check-shadowing: true
issues:
exclude-use-default: false
| イディオム | 説明 |
|---|---|
| インターフェースを受け取り、構造体を返す | 関数はインターフェースパラメータを受け取り、具体的な型を返す |
| エラーは値である | エラーを例外ではなく一級値として扱う |
| メモリ共有で通信しない | goroutine間の調整にチャネルを使用 |
| ゼロ値を有用にする | 型は明示的な初期化なしで機能すべき |
| 少しのコピーは少しの依存よりも良い | 不要な外部依存を避ける |
| 明確さは巧妙さよりも良い | 巧妙さよりも可読性を優先 |
| gofmtは誰の好みでもないが皆の友達 | 常にgofmt/goimportsでフォーマット |
| 早期リターン | エラーを最初に処理し、ハッピーパスのインデントを浅く保つ |
// Bad: Naked returns in long functions
func process() (result int, err error) {
// ... 50 lines ...
return // What is being returned?
}
// Bad: Using panic for control flow
func GetUser(id string) *User {
user, err := db.Find(id)
if err != nil {
panic(err) // Don't do this
}
return user
}
// Bad: Passing context in struct
type Request struct {
ctx context.Context // Context should be first param
ID string
}
// Good: Context as first parameter
func ProcessRequest(ctx context.Context, id string) error {
// ...
}
// Bad: Mixing value and pointer receivers
type Counter struct{ n int }
func (c Counter) Value() int { return c.n } // Value receiver
func (c *Counter) Increment() { c.n++ } // Pointer receiver
// Pick one style and be consistent
覚えておいてください: Goコードは最良の意味で退屈であるべきです - 予測可能で、一貫性があり、理解しやすい。迷ったときは、シンプルに保ってください。
Instinct-based learning system that observes sessions via hooks, creates atomic instincts with confidence scoring, and evolves them into skills/commands/agents. v2.1 adds project-scoped instincts to prevent cross-project contamination.
Orchestrate building a brand-new feature end to end — research, plan, TDD implementation, review, and gated commit — by delegating each phase to the matching ECC agent. Use when adding a capability that does not exist yet.
Orchestrate bootstrapping a working MVP from a design or spec document — ingest the doc, plan thin vertical slices, scaffold the first end-to-end slice, then TDD-implement, review, and gated commit. Use to turn an SDD/PRD into a running starting point.
Orchestrate altering an existing, working feature to new desired behavior — update its tests to the new spec, change the implementation to match, review, and gated commit. Use when behavior is not broken but should be different.
Orchestrate fixing a bug — reproduce it as a failing regression test, fix to green, review, and gated commit — by delegating each phase to the matching ECC agent. Use when existing behavior is broken or wrong.
Shared orchestration engine for the orch-* skill family. Defines the gated Research-Plan-TDD-Review-Commit pipeline, the size classifier, the agent map, and the two human gates that the orch-* operation skills delegate to. Not usually invoked directly.