golang random string

package main

import (  
  "math/rand"
  "time"
  "fmt"
)

const charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"

var seededRand *rand.Rand = rand.New(  
  rand.NewSource(time.Now().UnixNano()))

func StringWithCharset(length int, charset string) string {  
  b := make([]byte, length)
  for i := range b {
    b[i] = charset[seededRand.Intn(len(charset))]
  }
  return string(b)
}

func String(length int) string {  
  return StringWithCharset(length, charset)
}

func main() {
	fmt.Println(String(10))
}

// For higher performance see 
// https://stackoverflow.com/questions/22892120/how-to-generate-a-random-string-of-a-fixed-length-in-golang