code: func NewGenerator(seed int64) *Generator {
  	r := rand.New(rand.NewSource(seed))
  	return &Generator{
  		r:     r,
  		zs:    make(map[int]*rand.Zipf),
  		times: make(map[time.Time]time.Duration),
  		hsh:   sha1.New(),
  	}
  }
docs: // NewGenerator gets a new Generator