golang生成指定位数的字符串（数字、大小写字母）

package main
 
import(
    "fmt"
    "time"
    "@H_42_12@math/rand"
)
 
const (
    KC_RAND_KIND_NUM   = 0  // 纯数字
    KC_RAND_KIND_LOWER = 1  // 小写字母
    KC_RAND_KIND_UPPER = 2  // 大写字母
    KC_RAND_KIND_ALL   = 3  // 数字、大小写字母
)
 
// 随机字符串
func Krand(sizE int,kind int) []byte {
    ikind,kinds,result := kind,[][]int{[]int{10,48},[]int{26,97},65}},make([]byte,sizE)
    is_all := kind > 2 || kind < 0
    rand.Seed(time.Now().UnixNano())
    for i :=0; i < size; i++ {
        if is_all { // random ikind
            ikind = rand.Intn(3)
        }
        scope,base := kinds[ikind][0],kinds[ikind][1]
        result[i] = uint8(base+rand.Intn(scopE))
    }
    return result
}
 
func main(){
    fmt.Println("num:   " + String(Krand(16,KC_RAND_KIND_NUM)))
    fmt.Println("lower: " + String(Krand(16,KC_RAND_KIND_LOWER)))
    fmt.Println("upper: " + String(Krand(16,KC_RAND_KIND_UPPER)))
    fmt.Println("all:   " + String(Krand(16,KC_RAND_KIND_ALL)))
}

运行效果：
num: 1724754808278598
lower: rvuwvrmamuafuxpg
upper: RVUWVRMAMUAFUXPG
all: VWrA875Gg80U07GP