It's dying out in popular culture, but we certainly do. For example, a very quick Google search shows that Central Befordshire Council spells it that way, as does Heritage Ireland and Discover Hertford. Also The Guardian and The Independent (only two papers I have immediate access to).
And, of course, the good old Beeb. As one example, here's a news article: "Each offence would carry maximum penalties of five years imprisonment plus an unlimited fine on indictment or 12 months gaol plus a fine of up to £10k in summary cases."
But the best, and most definitive, place to check would of course be HMPS (the Prison Service). A quick search turns up this report: "The current site opened as a county gaol in 1847 and served as such until 1890 when it became a women’s prison. Two additional wings were built adjacent to the main prison in 1902, serving initially as an inebriates centre and, from the mid-1930s, as a borstal for girls. In 1959, the gaol was converted to accommodate adult male prisoners but its role was changed in 1961 to provide accommodation for young men between the ages of 17 and 21."; or indeed this report on Liverpool Prison from 2011: "HMP Liverpool, known locally as Walton Gaol, is a large, local prison for remand and convicted men mainly from the Merseyside area."
Indeed, the Prison Service itself also refers officially to gaolers with rules and guidelines such as:
...The nature of those held, the imbalance of power between detainee and gaoler and the fact that the work of the institution takes place behind high walls, out of sight, creates...
...c) if the payment is made to the gaoler, he shall sign a certificate of payment and send the amount to the court which made the committal order. ( ... it by post or otherwise to the gaoler...
...sign a certificate of payment and send it by post or otherwise to the gaoler; ( b) if the payment is made to the court which issued the warrant of committal after ... court shall make and sign a certificate of payment and send it by post or otherwise...
...Custody teams were drawn from among frontline operational response staff, and normally comprised three sergeants and two gaolers to cover the two suites. ... There was some training for gaolers as part of the borough s training cycle, but no civilian...
...Sergeants were supported by a small number of dedicated detention officers ( DDOs), who were permanent custody staff, and police constable gaolers, who were not permanent and had not benefited from ... Some gaolers could not input onto NSPIS,...
...The Hackney suites benefited from a clear local management structure. There were trained designated detention officers, but custody sergeants and police constable gaolers were not permanent and the latter lacked specific ... 2.7 Custody sergeants and...
...Other custody sergeants and gaolers were drawn from operational policing teams. ... Custody sergeants had attended nationally approved custody training, but PC gaolers had not....
I won't mention Oscar Wilde's famous ballad, as that's a little older.
So it may be true that it's dying out in popular culture, but when Her Majesty's Prison Service, the BBC, national newspapers, local councils, and others all spell it "gaol" and "gaoler" it's a pretty hard sell to claim that such spellings must be in an "parallel universe".
