Golang 单例模式的几种形式

1.非线程安全，虽然说是单例模式，但是如果实例正在创建中，此时多个线程同时访问，就会获得多个结果

package main

var instance *Singleton

type Singleton struct {

}

func Instance() *Singleton{

if instance == nil {

instance = &Singleton{}

}

return instance

}

加锁单例模式

package main

import "sync"

var (

instance *Singleton

mu sync.Mutex

)

type Singleton struct {

}

func Instance() *Singleton{

mu.Lock()

defer mu.Unlock()

if instance == nil {

instance = &Singleton{}

}

return instance

}

以下是参考他人的方法。思路很好

3.避免了每次加锁，提高了代码效率

package main

import "sync"

var (

instance *Singleton

mu sync.Mutex

)

type Singleton struct {

}

func Instance() *Singleton {

if instance == nil {

mu.Lock()

defer mu.Unlock()

if instance == nil {

instance = &Singleton{}

}

}

return instance

}

4.once实现

package main

import "sync"

var (

instance *Singleton

once sync.Once

)

type Singleton struct {

}

func Instance() *Singleton {

once.Do(func() {

instance = &Singleton{}

})

return instance

}