code: func (o *pdOracle) IsExpired(lockTS, TTL uint64) bool {
  	lastTS := atomic.LoadUint64(&o.lastTS)
  	return oracle.ExtractPhysical(lastTS) >= oracle.ExtractPhysical(lockTS)+int64(TTL)
  }
docs: // IsExpired returns whether lockTS+TTL is expired, both are ms. It uses `lastTS`
  // to compare, may return false negative result temporarily.