Not all goats will bleat or whine at night as long as they're healthy and happy.
When goats bleat, whine or cry at night then it means that something is wrong either with the goats health, the goat itself or something is trying to harm the goat.
Goat bleating at night in healthy happy goats is not normal so if they're bleating you need to check on the goats or get them checked out and be sure that nothing is out there harming the goat or the goat is in good health.