随机字符串
package utils
import (
"math/rand"
"time"
)
const (
RandKindNum = 1 << 0
RandKindLower = 1 << 1
RandKindUpper = 1 << 2
RandKindAll = RandKindNum | RandKindLower | RandKindUpper
)
var randSource = rand.New(rand.NewSource(int64(time.Now().Nanosecond(