Satsu

Current tech-wise? We'd be toast, plain and simple. (Just look at the material currently available on the sun's current life cycle. Its expansion would consume our world. Mars would be turned into a Mercury like planet, iirc, etc.)

Unless, there's some nice aliens out there capable of undoing the damage that our current level of cryo tends to cause. And that's about the best case scenario. Sleeper ship with folks loaded into cryo tubes, with a nuclear power plant to keep everything running.

Not sure, if it would have enough speed to outrun the expansion, but that's another issue.

As for what people would do? Riot, start wars.. End of times stuff.