相似单例模式，享元模式也是经过共享对象来提升性能。区别在于：数据库

• 单例模式只保存一个对象的实例，例如客户端的数据库链接对象。
• 享元模式保存一类对象的实例，例如服务端的线程池、链接池等。

Golang 示例

package main

import (
	"fmt"
)

type Connect struct {
	name string
}
func NewConnect(name string) *Connect {
	return &Connect{name}
}
type ConnectFactory struct {
	pool map[string]*Connect
}
func NewConnectFactory() *ConnectFactory {
	return &ConnectFactory{pool:map[string]*Connect{}}
}
func (cf *ConnectFactory) GetConnect(key string) *Connect {
	if _, ok := cf.pool[key]; !ok {
		// ... connect
		c := NewConnect(key)
		fmt.Println("NewConnect success")
		cf.pool[key] = c
	}
	return cf.pool[key]
}

func main() {
	cf := NewConnectFactory()
	c1 := cf.GetConnect("con1")
	fmt.Println(c1.name)
	c1 = cf.GetConnect("con1")
	fmt.Println(c1.name)
	c2 := cf.GetConnect("con2")
	fmt.Println(c2.name)
}