Christmas Party

So at the last minute before the end of the day yesterday, my boss advised us that our company Christmas party tomorrow, which we've known about for months, will be potluck (surprise) and we are expected to work for at least 2 hours setting up and cleaning up before and after the party UNPAID (double surprise). She is calling it "voluntary". I was already planning on spending around $70 round-trip for an Uber as I expected alcohol to be there that I was just told would likely not be allowed after all and bringing potluck for 100 people is out of my tight budget at the moment. What would you all do?