How to Separate Business Logic from Infrastructure in Go

Separate business logic from infrastructure in Go by defining interfaces for external dependencies and injecting concrete implementations via dependency injection. This ensures your core logic depends only on abstractions, not specific tools like databases or HTTP clients.

// Define an interface for the infrastructure dependency
type UserRepository interface {
    GetByID(id string) (*User, error)
}

// Business logic depends only on the interface
type UserService struct {
    repo UserRepository
}

func NewUserService(repo UserRepository) *UserService {
    return &UserService{repo: repo}
}

// Infrastructure implementation satisfies the interface
type PostgresUserRepo struct {
    db *sql.DB
}

func (r *PostgresUserRepo) GetByID(id string) (*User, error) {
    // Database logic here
    return nil, nil
}

// Wire them together in main()
func main() {
    repo := &PostgresUserRepo{db: openDB()}
    service := NewUserService(repo)
    // Use service
}

Separating business logic from infrastructure in Go keeps your core rules distinct from the tools used to run them. Think of it like a recipe that doesn't care if you cook on a gas stove or an electric one. You can swap the stove without rewriting the recipe, making your code easier to test and change.