Maybe it's just me, but I feel that the word jailer itself, however it's spelled, has a bit of an 'old-fashioned' ring to it.
The word 'Prison' now seems to be much more common than jail.
(Not in 'Monopoly' of course which still has its 'Jail'!)
Type jailer on Wikipedia and you are directed to a page headed 'Prison Officer' which lists some of the terms used in different parts of the world - 'corrections officer', 'correctional officer', 'detention officer' etc.
Perhaps in a few years the word jailer will have followed some of its earlier synonyms such as turnkey into near oblivion.