peer_heap.go
func (ph *peerHeap) pushPeer(peerScore *peerScore) {
	ph.order++
	newOrder := ph.order
	// randRange will affect the deviation of peer's chosenCount
	randRange := ph.Len()/2 + 1
	peerScore.order = newOrder + uint64(ph.rng.Intn(randRange))
	heap.Push(ph, peerScore)
}
func (ph *peerHeap) pushPeer(peerScore *peerScore) {
	ph.order++
	newOrder := ph.order
	// randRange will affect the deviation of peer's chosenCount
	randRange := ph.Len()/2 + 1
	peerScore.order = newOrder + uint64(ph.rng.Intn(randRange))
	heap.Push(ph, peerScore)
}
// pushPeer pushes the new peer into the heap.