PassKit's answer is correct, but I wanted to add some more detail.
First off, just to confirm, your ticket will still be valid, but you'll lose the extra bag and priority boarding. Those privileges only apply if you're an active Delta co-branded cardholder at the time of the flight. Delta's computers will be aware of whether you are an active cardholder or not and the boarding zone and extra free checked bag will be added automatically if you are. If you are an active cardholder, this will also be printed at the top of your boarding pass. Additionally, these benefits apply to all people on your reservation, for a total of up to nine people. So, if you're traveling round-trip with at least one other person and both checking a bag, the bag fee benefit alone is worth more than the card's annual fee (though only by $5 in that case.)
It's unlikely that you'd be able to successfully flash the cancelled card, since, as I mentioned, Delta's computers are aware of if the card is active or not and these benefits are granted automatically, not manually by the gate or check-in desk agents. Maybe this would work if you cancelled the card after printing your boarding pass, but that would only work within 24 hours of the flight (and, even then, I still wouldn't count on it.)
In addition to the suggestion of calling and asking if they can waive the annual fee (which may or may not work,) if your flight is soon after when you'd need to pay the fee, you can try waiting until after the flight to cancel it. AmEx will normally refund the entire annual fee if you cancel within a few weeks after the anniversary date. I think they also refund a pro-rated annual fee if you cancel later, but I could be remembering that incorrectly.
If you usually fly Delta domestically with at least one other person on your reservation at least once per year, one option you might want to consider is switching from the Gold Delta SkyMiles card to the Platinum one. While the annual fee is higher ($195 vs. $95,) the Platinum Delta co-branded card includes a free companion economy-class domestic (within the continental 48 states) round-trip once per year on your cardholder anniversary date, which can be used for up to a year from that date. While you don't get said voucher during the first year as a cardholder, you would get another sign-up bonus, which will usually be worth even more than the voucher (I got a 60,000 SkyMiles + 10,000 MQM sign-up bonus for it, for example.) Since domestic round-trips are generally worth more than $195, the voucher alone more than covers the cost of the annual fee, provided you use it. For a trans-con round-trip, this benefit alone is usually worth $400-$500, for example.