Critical Patterns

Error Handling (REQUIRED)

// ✅ ALWAYS: Explicit error handling result, err := doSomething() if err != nil { return fmt.Errorf("doSomething failed: %w", err) }

// ❌ NEVER: Ignore errors result, _ := doSomething()

Naming Conventions (REQUIRED)

// ✅ ALWAYS: Short, clear names func (u *User) Name() string { return u.name }

// Package-level: unexported unless needed type userService struct { ... } // internal type UserService struct { ... } // exported

// ❌ NEVER: Java-style names func (user *User) GetUserName() string { ... }

Context Propagation (REQUIRED)

// ✅ ALWAYS: Pass context as first parameter func GetUser(ctx context.Context, id string) (*User, error) { select { case <-ctx.Done(): return nil, ctx.Err() default: return db.FindUser(ctx, id) } }

Decision Tree

Need to share state? → Use channels, not shared memory Need cancellation? → Use context.Context Need cleanup? → Use defer Need interface? → Define where used, not implemented Need configuration? → Use functional options

Code Examples

Functional Options

type ServerOption func(*Server)

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

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

// Usage server := NewServer(WithPort(9000))

Goroutines with Error Group

import "golang.org/x/sync/errgroup"

g, ctx := errgroup.WithContext(ctx)

g.Go(func() error { return fetchUsers(ctx) })

g.Go(func() error { return fetchOrders(ctx) })

if err := g.Wait(); err != nil { return err }

Commands

go mod init myapp # Initialize module go run . # Run application go build -o bin/app . # Build binary go test ./... # Run all tests go test -race ./... # Race detection golangci-lint run # Linting

Resources

• API Best Practices: api-best-practices.md

• Effective Go: effective-go.md

• Microservices: microservices.md