enums.go

type User enum {
  Authenticated struct {
    Name string
  }
  Anonymous struct {}
}

// and/or

type Authenticated struct {
  Name string
}

type Anonymous struct {}

type User enum {
  Authenticated
  Anonymous
}

vanilla.go

type User interface {
  isUser()
}

type Authenticated struct {
  Name string
}

func (Authenticated) isUser(){}


type Anonymous struct {}

func (Anonymous) isUser(){}