Hands-On Dependency Injection in Go

JIT injection

Have you ever written an object and injected a dependency that you knew was only going to have one implementation? Perhaps you have injected the database handling code into the business logic layer, as shown in the following code:

func NewMyLoadPersonLogic(ds DataSource) *MyLoadPersonLogic {   return &MyLoadPersonLogic{      dataSource: ds,   }}type MyLoadPersonLogic struct {   dataSource DataSource}// Load person by supplied IDfunc (m *MyLoadPersonLogic) Load(ID int) (Person, error) {   return m.dataSource.Load(ID)}

Have you ever added a dependency to your constructor for the sole purpose of mocking it out during testing? This is shown in the following code:

func NewLoadPersonHandler(logic LoadPersonLogic) *LoadPersonHandler {   return