Slice reuse issue in ExpDecaySample.update

[jerryjxj]

Suspecious code in file sample.go

func (s *ExpDecaySample) update(t time.Time, v int64) {
	s.mutex.Lock()
	defer s.mutex.Unlock()
	s.count++
	if s.values.Size() == s.reservoirSize {
		s.values.Pop()
	}
	s.values.Push(expDecaySample{
		k: math.Exp(t.Sub(s.t0).Seconds()*s.alpha) / rand.Float64(),
		v: v,
	})
	if t.After(s.t1) {
		values := s.values.Values()
		t0 := s.t0
		s.values.Clear()
		s.t0 = t
		s.t1 = s.t0.Add(rescaleThreshold)
		for _, v := range values {
			v.k = v.k * math.Exp(-s.alpha*s.t0.Sub(t0).Seconds())
			s.values.Push(v)
		}
	}
}

In if t.After(s.t1) {} block, values and s.values share the same memory block, because s.values.Clear() doesn't abandon the address (The address of the inherent Array) actually. s.values.Push(v) might overwrite values