Golangランダム値生成アルゴリズム

package main

import (
    "crypto/rand"
    "fmt"
)

var strstr = []byte("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")

func GetUID() string {
    data := make([]byte, 16)
    _, err := rand.Read(data)
    if err != nil {
        panic(err)
    }
    uuid := fmt.Sprintf("%X-%X-%X-%X-%X", data[0:4], data[4:6], data[6:8], data[8:10], data[10:])
    return uuid
}

func GetString(size int) string {
    data := make([]byte, size)
    out := make([]byte, size)
    buffer := len(strstr)
    _, err := rand.Read(data)
    if err != nil {
        panic(err)
    }
    for id, key := range data {
        x := byte(int(key) % buffer)
        out[id] = strstr[x]
    }
    return string(out)
}

func main(){
    fmt.Println(GetUID())
    fmt.Println(GetString(8))
}