// Recommended
package user
package handler
package service

// Not recommended
package UserService
package user_service
package utils

user/
├── user_handler.go
├── user_service.go
├── user_dao.go
└── user_test.go

project/
├── cmd/                    # Main entry point
│   └── server_main.go
├── internal/               # Private code
│   ├── handler/
│   ├── service/
│   ├── dao/
│   ├── model/
│   └── middleware/
├── pkg/                    # Public code
└── api/                    # API definitions

// Recommended
type Reader interface {
    Read(p []byte) (n int, err error)
}

type UserService interface {
    Register(req *RegisterRequest) (*User, error)
    Login(req *LoginRequest) (*User, error)
}

// Not recommended
type UserInterface interface {}
type IUserService interface {}

// Recommended
type UserService struct {}
type UserHandler struct {}
type RegisterRequest struct {}

// Not recommended
type user_service struct {}
type SUserService struct {}
type UserModel struct {}

// Recommended
func (s *UserService) Register(req *RegisterRequest) (*User, error)
func (s *UserService) GetUserByID(id uint) (*User, error)
func (s *UserService) IsEmailExists(email string) bool

// Not recommended
func (s *UserService) register_user()
func (s *UserService) get_user_by_id()
func (s *UserService) CheckEmailExists() // Should use Is/Has

// Recommended
const (
    StatusActive   = "1"
    StatusInactive = "0"
    MaxRetryCount  = 3
)

// Not recommended
const (
    STATUS_ACTIVE = "1"  // Not all uppercase
    status_active = "1"  // Not all lowercase
)

// Recommended
var (
    ErrNotFound      = errors.New("not found")
    ErrInvalidInput  = errors.New("invalid input")
    ErrUnauthorized  = errors.New("unauthorized")
)

// Recommended
type HTTPHandler struct {}
var URL string
func GetHTTPClient() {}
func ParseJSON() {}

// Not recommended
type HttpHandler struct {}
var Url string
func GetHttpClient() {}

project-name/
├── cmd/                    # Main programs
│   └── app_name/
│       └── main.go
├── internal/               # Private code
│   ├── handler/           # HTTP handlers
│   ├── service/           # Business logic
│   ├── repository/        # Data access
│   ├── model/             # Data models
│   └── config/            # Configuration
├── pkg/                    # Public code
├── api/                    # API definitions
├── configs/               # Config files
├── scripts/               # Scripts
├── docs/                  # Documentation
├── go.mod
└── go.sum