code: func Random(min int64, max int64) float64 {
  
  	if max <= min {
  		panic(fmt.Sprintf("invalid range %d >= %d", max, min))
  	}
  	decimal := rand.Float64()
  
  	if max <= 0 {
  		return (float64(rand.Int63n((min * -1)-(max * -1))+(max * -1)) + decimal) * -1
  	}
  	if min < 0 && max > 0 {
  		if rand.Int()%2 == 0 {
  			return float64(rand.Int63n(max)) + decimal
  		} else {
  			return (float64(rand.Int63n(min * -1)) + decimal) * -1
  		}
  	}
  	return float64(rand.Int63n(max-min)+min) + decimal
  }
docs: //生成指定大小的随机数.