golang-constructors-blog-2-3.go

// Service Package
type Service interface {
    CountNumUsers() int
}
type service struct {
    Repository *UserRepository
}
func (s service) CountNumUsers() int {
    return s.Repository.Count()
}
func New(r UserRepository) Service {
    return service{Repository: &r}
}

// Package 2
r := Repository.New(db)
s := Service.New(*r)