go中for range的坑以及解决方案

func fr1() {
	arr := []int{1, 2, 3}
	for _, val := range arr {
		go func() {
            time.Sleep(time.Millisecond * 100)
			fmt.Println(val)
		}()
	}
	time.Sleep(time.Second)
}
//输出结果：3 3 3 


func fr2() {
	arr := [2]int{1, 2}
	arrnew := []*int{}
	for _, val := range arr {
		arrnew = append(arrnew, &v)
	}

	fmt.Println(*arrnew[0], *arrnew[1])
	//输出结果: 2 2
}

func fr1() {
	values := []int{1, 2, 3, 4, 5}
	for _, val := range values {
        //在这加入临时变量
		val := val 
		go func() {
			time.Sleep(time.Millisecond * 100)
			fmt.Println(val)
		}()
	}
	time.Sleep(time.Second)
}
//输出结果：2 3 1 4 5 或 5 3 4 1 2 等无序结果


//===========================或者=============================

func fr1() {
	values := []int{1, 2, 3, 4, 5}
	for _, val := range values {
        //传入变量
		go func(val int) {
			time.Sleep(time.Millisecond * 100)
			fmt.Println(val)
		}(val)
	}
	time.Sleep(time.Second)
}
//输出结果：2 3 1 4 5 或 5 3 4 1 2 等无序结果

go env -w GOEXPERIMENT=loopvar
或
$env:GOEXPERIMENT="loopvar"

> go env
set GO111MODULE=on
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\Administrator\AppData\Local\go-build
set GOENV=C:\Users\Administrator\AppData\Roaming\go\env
set GOEXE=.exe
set GOEXPERIMENT=loopvar
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=C:\Users\Administrator\go\pkg\mod