People who tell you that it also means "goodbye" are correct. It is an alternate form of "cheerio". It's not in popular use now, but it's recorded with this s

People who tell you that it also means "goodbye" are correct. It is an alternate form of "cheerio". It's not in popular use now, but it's recorded with this sense in mid-20th-century dictionaries. Indeed, one 21st century Partridge's records "cheers" meaning "goodbye" (1960s) as pre-dating "cheers" meaning "thank you" (1970s).