问题：Golang 使用UnixNano()作为唯一键id，在高并发环境下出现重复，

package main

import (

"fmt"

"github.com/fwhezfwhez/go-queue"

"runtime"

"strconv"

"sync"

"time"

)

var mutex sync.Mutex

func main() {

runtime.GOMAXPROCS(runtime.NumCPU())

wg := sync.WaitGroup{}

var loopCount int = 5000

var queue = Queue.NewEmpty()

for i := 0; i < loopCount; i++ {

wg.Add(1)

go func(in int, q *Queue.Queue) {

tmp := getNum()

q.SafePush(tmp)

fmt.Println("finish " + strconv.Itoa(in) + ",produce:" + strconv.FormatInt(tmp, 10))

wg.Done()

}(i, queue)

}

wg.Wait()

//queue.Print() // 输入所有UUID

if (queue.ValidLength() == loopCount) {

fmt.Println("生成", loopCount, "个UUID数量，没发现重复，继续测试。")

fmt.Println("备注：若运行没有输出，证明是有重复，程序结束。")

}

}

func getNum() int64 {

mutex.Lock()

defer mutex.Unlock()

return time.Now().UnixNano()

}

运行结果，发现重复：

改进版本-1：数字UUID改进版 (unixNano + hashCode(uuid))

package main

import (

"fmt"

"github.com/fwhezfwhez/go-queue"

uuid "github.com/satori/go.uuid"

"hash/crc32"

"runtime"

"strconv"

"sync"

"time"

)

var mutex sync.Mutex

func main() {

runtime.GOMAXPROCS(runtime.NumCPU())

wg := sync.WaitGroup{}

var loopCount int = 5000

var queue = Queue.NewEmpty()

for i := 0; i < loopCount; i++ {

wg.Add(1)

go func(in int, q *Queue.Queue) {

tmp := getNum()

q.SafePush(tmp)

fmt.Println("finish " + strconv.Itoa(in) + ",produce:" + tmp)

wg.Done()

}(i, queue)

}

wg.Wait()

//queue.Print() // 输入所有UUID

if (queue.ValidLength() == loopCount) {

fmt.Println("生成", loopCount, "个UUID数量，没发现重复，继续测试。")

fmt.Println("备注：若运行没有输出，证明是有重复，程序结束。")

}

}

//改进方法

func getNum() string {

mutex.Lock()

defer mutex.Unlock()

currentTime := time.Now()

timestamp := currentTime.UnixNano()

uuid,_ := uuid.NewV4()

uuidHash := int(crc32.ChecksumIEEE([]byte(uuid.String())))

if -uuidHash >= 0 {

uuidHash = -uuidHash

}

uuidStr := strconv.FormatInt(timestamp,10)+strconv.Itoa(uuidHash)

return uuidStr

}