Golang Promise simulation

main.go

func main() {
    person := new(Person)
    person.Name = "Carmine"

    SavePerson(person).Then(func(obj interface{}) error {
	fmt.Printf("Successfully created %v\n", obj)
	return nil
    }, func(err error) {
	fmt.Printf("Failed to create %v\n", err)
    }).Then(func(obj interface{}) error {
        fmt.Printf("Chain - Do something after Person is created")
	return nil
    }, func(err error) {
	fmt.Printf("Failed %s", err.Error())
    })
}

promise.go

func (promise *Promise) Then(success func(interface{}) error, failure func(error)) *Promise {
    result := new(Promise)
    result.resolverCh = make(chan interface{})
    result.rejectorCh = make(chan error)

    go func() {
	select {
	case res := <-promise.resolverCh:
	    err := success(res)
	    if err == nil {
		result.resolverCh <- res
	    } else {
		result.rejectorCh <- err
	    }
	case err := <-promise.rejectorCh:
	    failure(err)
	    result.rejectorCh <- err
	}
    }()
  
    return result
}

savePerson.go

func SavePerson(person *Person) *Promise {
    promise := new(Promise)
    promise.resolverCh = make(chan interface{})
    promise.rejectorCh = make(chan error)

    go func() { 
        res, err := db.Save(person) // This method is not shown here - imagine it updates a db
    
        if err != nil {
          promise.rejectorCh <- err
        } else {
          promise.resolverCh <- res
        }
    }()
  
    return promise
}