I wouldn’t be too keen on something like WD40 in an ignition barrel. It will attract dirt once the key is removed. Graphite power would be a better option.
If you can tak the bike to a locksmith that would probably be the best option. I had a key stuck in a pannier once and the locksmith got it out easily.
So, it may have been literally frozen in the cylinder. I walked out around 6pm and the key popped right out. Rode home, popped in/out just fine. I cleaned a little bit of lint/grease/something out of one side that MIGHT have been frozen and locking the key in place, but really no juicy payoff here. We were below freezing all day until late afternoon, so I figure sun, warm, etc.