golang生成指定位数的随机数的方法

package main
import (
  "fmt"
  "math/rand"
  ）
func CreateCaptcha() string {
  return fmt.Sprintf("%06v", rand.New(rand.NewSource(time.Now().UnixNano())).Int31n(1000000))
}
func main(){
  fmt.Println(CreateCaptcha() )
}

func CreateCaptcha() string {
  return fmt.Sprintf("%08v", rand.New(rand.NewSource(time.Now().UnixNano())).Int31n(100000000))
}