We've been watching "Turn" on Netflix, which is a 4 season series dealing mainly with Washington's spies, but which touches on, or forces connections to, episodes in the Revolution which are more commonly known. (I think it makes very generous use of "dramatic license".)
Anyhow, in the episode ending season 2, the African-American who was freed by Capt. Simcoe and enlisted in his Queen's Rangers takes the son of the enslaved maid to Major Andre from Setauket into York City to rejoin his mother. (The maid's been doing a little spying for the rebels on the side.) Needless to say, the British soldier loves the maid and urges her to flee with him to Canada so they can both be free.
I wondered about the accuracy of that so I did a little researching on the internet.
Sure enough, slavery in Canada lasted until 1834, when it was abolished throughout the empire.
But wait, it's not that simple. "Lower Canada" was originally Quebec, founded by the French until the Brits won it by conquest in the French and Indian War. "Upper Canada" became today's Ontario and was mostly settled by the English.
Reading between the lines it seems likely the Brits just kept the old French laws, including those pertaining to slavery at the start. And in "Lower Canada" they might have kept the laws until 1834. But by 1790's slavery in Upper Canada was being questioned, and a courageous troublemaker named Chloe Cooley resisted being sold as a slave into New York. That resulted in an act restricting the importation of slaves and promising freedom to children born after 1793. But the act only applied to Upper Canada.
Based on skimming the second article I linked to, slaves in the thirteen colonies should not have seen Canada as the promised land of freedom before 1793.