code: func init() {
  	// algorithm taken from https://github.com/zenazn/goji/blob/master/web/middleware/request_id.go#L44-L50
  	var buf [12]byte
  	var b64 string
  	for len(b64) < 10 {
  		rand.Read(buf[:])
  		b64 = base64.StdEncoding.EncodeToString(buf[:])
  		b64 = strings.NewReplacer("+", "", "/", "").Replace(b64)
  	}
  	reqPrefix = string(b64[0:10])
  }
docs: // Initialize common prefix on process startup.