Implement proxy pattern in golang

proxy_pattern.go

package main

import (
	"log"
)

type Wizard struct {
	Name string
}

type WizardTower interface {
	Enter(w Wizard)
}

type IvyTower struct{}

func (i IvyTower) Enter(w Wizard) {
	log.Printf("%s enter tower", w.Name)
}

// ProxyTower implementation
type ProxyTower struct {
	Tower            WizardTower
	NUMBER_OF_WIZARD int8
}

// Enter applies proxy policy
func (proxy *ProxyTower) Enter(w Wizard) {
	if proxy.NUMBER_OF_WIZARD < 2 {
		proxy.Tower.Enter(w)
		proxy.NUMBER_OF_WIZARD++
	} else {
		log.Printf("Number of wizard is limited")
	}
}

func main() {
	log.Printf("hello world")
	p := ProxyTower{Tower: IvyTower{}}
	p.Enter(Wizard{Name: "Red wizard"})
	p.Enter(Wizard{Name: "White wizard"})
	p.Enter(Wizard{Name: "Black wizard"})
	p.Enter(Wizard{Name: "Brown wizard"})
}