import (
 "math/rand"
)

var chars = []rune(" abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890")

func randString(n int) string {
  b := make([]rune, n)
  for i := range b {
    b[i] = chars[rand.Intn(len(chars))]
  }
  return string(b)
}