Create random string with pre-defined size.

util.go

import "crypto/rand"

func RandStr(strSize int) (ret string, err error) {
	alphanum := "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
	var bytes = make([]byte, strSize)
	_, err = rand.Read(bytes)
	if err != nil {
		return
	}
	for k, v := range bytes {
		bytes[k] = alphanum[v%byte(len(alphanum))]
	}
	ret = string(bytes)
	return
}