Go Advanced Topics

Design Patterns

Creational Patterns

• Factory Method: Creates objects without exposing the instantiation logic

  type PaymentMethod interface {
      Pay(amount float64)
  }
  
  func CreatePayment(method string) PaymentMethod {
      switch method {
      case "credit":
          return &CreditCardPayment{}
      case "debit":
          return &DebitCardPayment{}
      default:
          return &CashPayment{}
      }
  }

• Abstract Factory: Provides an interface for creating families of related objects

• Singleton: Ensures a class has only one instance

  type singleton struct {}
  var instance *singleton
  var once sync.Once
  
  func GetInstance() *singleton {
      once.Do(func() {
          instance = &singleton{}
      })
      return instance
  }

• Builder: Separates object construction from its representation

• Object Pool: Pre-instantiates and maintains a group of objects

Structural Patterns

• Adapter: Converts interface of a class into another interface clients expect

  type LegacyPrinter interface {
      Print(s string) string
  }
  
  type ModernPrinter interface {
      PrintStored() string
  }
  
  type PrinterAdapter struct {
      OldPrinter LegacyPrinter
      Msg string
  }
  
  func (p *PrinterAdapter) PrintStored() string {
      return p.OldPrinter.Print(p.Msg)
  }

• Bridge: Separates an object's interface from its implementation

  type DrawAPI interface {
      DrawCircle(x, y, radius int)
  }
  
  type Shape struct {
      DrawAPI DrawAPI
  }
  
  type Circle struct {
      Shape
      X, Y, Radius int
  }
  
  func (c *Circle) Draw() {
      c.DrawAPI.DrawCircle(c.X, c.Y, c.Radius)
  }

• Composite: Composes objects into tree structures

• Decorator: Adds responsibilities to objects dynamically

• Facade: Provides a unified interface to a set of interfaces

Behavioral Patterns

• Observer: Defines a one-to-many dependency between objects

  type Observer interface {
      Update(string)
  }
  
  type Subject struct {
      observers []Observer
      state     string
  }
  
  func (s *Subject) Attach(o Observer) {
      s.observers = append(s.observers, o)
  }
  
  func (s *Subject) NotifyAll() {
      for _, observer := range s.observers {
          observer.Update(s.state)
      }
  }

• Strategy: Defines a family of algorithms and makes them interchangeable

  type Strategy interface {
      Execute(int, int) int
  }
  
  type Addition struct{}
  func (Addition) Execute(a, b int) int { return a + b }
  
  type Multiplication struct{}
  func (Multiplication) Execute(a, b int) int { return a * b }
  
  type Context struct {
      strategy Strategy
  }
  
  func (c *Context) SetStrategy(s Strategy) {
      c.strategy = s
  }

• Command: Encapsulates a request as an object

• State: Allows an object to alter its behavior when its internal state changes

• Iterator: Provides a way to access elements sequentially

Performance Optimization

Memory Optimization

• Memory pooling: Using sync.Pool for frequently allocated objects

  var bufferPool = sync.Pool{
      New: func() interface{} {
          return new(bytes.Buffer)
      },
  }
  
  func processData(data []byte) {
      buffer := bufferPool.Get().(*bytes.Buffer)
      defer bufferPool.Put(buffer)
      buffer.Reset()
      // Use buffer...
  }

• Object reuse: Reusing objects to reduce GC pressure

• Reducing allocations: Using stack allocation when possible

• Proper data structures: Choosing appropriate data structures for performance

CPU Optimization

• Profiling techniques
• Benchmarking
• Concurrency optimization
• Algorithm efficiency

Network Optimization

• Connection pooling
• Keep-alive connections
• Protocol optimization
• Batch processing

Security Best Practices

Input Validation

• Sanitizing user input
• Type validation
• Size limits
• Format validation

Authentication & Authorization

• JWT implementation: Secure token-based authentication

  import "github.com/golang-jwt/jwt"
  
  func createToken(userID string, secret []byte) (string, error) {
      token := jwt.New(jwt.SigningMethodHS256)
      claims := token.Claims.(jwt.MapClaims)
      claims["user_id"] = userID
      claims["exp"] = time.Now().Add(24 * time.Hour).Unix()
      return token.SignedString(secret)
  }

• OAuth integration: Third-party authentication support

• Role-based access control: Managing user permissions

• Session management: Secure session handling

Cryptography

• Secure random numbers
• Password hashing
• Data encryption
• TLS configuration

Integration Patterns

Database Integration

• Connection pooling
• Query optimization
• Transaction management
• ORM best practices

Microservices

• Service discovery
• Load balancing
• Circuit breaking
• API gateway patterns

Message Queues

• Publisher/Subscriber
• Message brokers
• Event sourcing
• CQRS pattern

Advanced Language Features

Reflection

• Type introspection
• Dynamic method calls
• Struct tag parsing
• Code generation

Assembly Integration

• Writing assembly
• Calling assembly
• Performance considerations
• Platform specifics

CGO

• C integration
• Memory management
• Type mapping
• Performance impact