go

Go

Overview

Go programming patterns including concurrency, error handling, and idiomatic Go code.

Basic Patterns

Structs and Methods

package main

import (
	"encoding/json"
	"fmt"
	"time"
)

// Struct definition
type User struct {
	ID        string    `json:"id"`
	Email     string    `json:"email"`
	Name      string    `json:"name"`
	CreatedAt time.Time `json:"created_at"`
	metadata  map[string]interface{} // unexported (private)
}

// Constructor function
func NewUser(email, name string) *User {
	return &User{
		ID:        generateID(),
		Email:     email,
		Name:      name,
		CreatedAt: time.Now(),
		metadata:  make(map[string]interface{}),
	}
}

// Value receiver (for read-only)
func (u User) FullName() string {
	return u.Name
}

// Pointer receiver (for mutations or large structs)
func (u *User) SetMetadata(key string, value interface{}) {
	u.metadata[key] = value
}

// Embedding (composition)
type Admin struct {
	User        // Embedded struct
	Permissions []string
}

func (a *Admin) HasPermission(perm string) bool {
	for _, p := range a.Permissions {
		if p == perm {
			return true
		}
	}
	return false
}

Interfaces

// Interface definition
type Repository interface {
	Find(id string) (*User, error)
	FindAll() ([]*User, error)
	Create(user *User) error
	Update(user *User) error
	Delete(id string) error
}

// Interface implementation (implicit)
type MemoryRepository struct {
	users map[string]*User
}

func NewMemoryRepository() *MemoryRepository {
	return &MemoryRepository{
		users: make(map[string]*User),
	}
}

func (r *MemoryRepository) Find(id string) (*User, error) {
	user, ok := r.users[id]
	if !ok {
		return nil, ErrNotFound
	}
	return user, nil
}

func (r *MemoryRepository) Create(user *User) error {
	r.users[user.ID] = user
	return nil
}

// Compile-time interface check
var _ Repository = (*MemoryRepository)(nil)

// Empty interface (any type)
func PrintAny(v interface{}) {
	fmt.Printf("%v\n", v)
}

// Type assertion
func ProcessValue(v interface{}) {
	switch val := v.(type) {
	case string:
		fmt.Println("String:", val)
	case int:
		fmt.Println("Int:", val)
	case *User:
		fmt.Println("User:", val.Name)
	default:
		fmt.Println("Unknown type")
	}
}