单例

懒汉模式

package main

import (
	"fmt"
	"sync"
)

type Singleton struct {
	data string
}

var instance *Singleton
var once sync.Once

func getInstance() *Singleton {
	once.Do(func() {
		instance = &Singleton{"Lazy Initialization"}
	})
	return instance
}

func main() {
	instance1 := getInstance()
	fmt.Println(instance1.data)

	instance2 := getInstance()
	fmt.Println(instance2.data)
}

恶汉模式

package main

import "fmt"

type Singleton struct {
	data string
}

var instance *Singleton = &Singleton{"Eager Initialization"}

func getInstance() *Singleton {
	return instance
}

func main() {
	instance1 := getInstance()
	fmt.Println(instance1.data)

	instance2 := getInstance()
	fmt.Println(instance2.data)
}