Unless it's your oldest account it's not going to hurt your credit to close it. It will still age for 10 years under the FICO 8 algorithm.
I close cards right and left and my score isn't affected by it.
FICO 8 calculates "average age of accounts" as total months of all accounts on your credit report (both open and closed) from the open dates to the present, divided by the number of all accounts on your report. "Average age of accounts" is what they use in their scoring algorithm. They also factor in "age of oldest account" in their scoring algorithm which is why you shouldn't close your oldest account because it will drop off your credit report after 10 years. Closed accounts only stay on your credit report for 10 years.
FICO08 factors closed cards into your average account age, until they fall off 10 years from closing at which point they are obviously no longer included in the average.
Never close your oldest credit line if you can avoid it, because in 10 years that WILL hurt your credit history.
If you were loaning money to someone wouldn't you want them to have a history of paying back loans to others?
A closed credit line will drop off your report after 10 years after you closed it (or is it 10 years after open date? I don't know which!)