code: func init() {
  	hostname, err := os.Hostname()
  	if hostname == "" || err != nil {
  		hostname = "localhost"
  	}
  	var buf [12]byte
  	var b64 string
  	for len(b64) < 10 {
  		rand.Read(buf[:])
  		b64 = base64.StdEncoding.EncodeToString(buf[:])
  		b64 = strings.NewReplacer("+", "", "/", "").Replace(b64)
  	}
  
  	prefix = fmt.Sprintf("%s/%s", hostname, b64[0:10])
  }
docs: // A quick note on the statistics here: we're trying to calculate the chance that
  // two randomly generated base62 prefixes will collide. We use the formula from
  // http://en.wikipedia.org/wiki/Birthday_problem
  //
  // P[m, n] \approx 1 - e^{-m^2/2n}
  //
  // We ballpark an upper bound for $m$ by imagining (for whatever reason) a server
  // that restarts every second over 10 years, for $m = 86400 * 365 * 10 = 315360000$
  //
  // For a $k$ character base-62 identifier, we have $n(k) = 62^k$
  //
  // Plugging this in, we find $P[m, n(10)] \approx 5.75%$, which is good enough for
  // our purposes, and is surely more than anyone would ever need in practice -- a
  // process that is rebooted a handful of times a day for a hundred years has less
  // than a millionth of a percent chance of generating two colliding IDs.