Welcome to FlyerTalk, Redbeanz.

5 kg empty seems quite heavy for a carry-on bag.

The clear immediate solution is to get a very light bag (even it's just a strong plastic garbage bag or something like that) for this trip and put your most important things in it, and check the heavy bag.

(I think of this because a few years after 9-11, the UK had a temporary policy that only one plastic garbage-type bag could be carried through security for a month or so, because they didn't have the screening capacity for suddenly increased screening needs. To do this day I carry such a plastic garbage-type bag in my carry-on bag as a just-in-case backup.)

The long-term solution is to replace that heavy carry-on bag with a much lighter one. They certainly exist, because it depends on the construction and the materials how heavy the bag itself is.

Also, does GOL count the 5kg for carryon "bags", or also for backpacks? Some airlines fill weigh a bag you're carrying but not make you take something off your back (unless it "looks" very heavy perhaps). In the US you're allows a "carryon" plus a "personal item", and you haven't mentioned the "personal item". (Gosh, I fit my camera and laptop and some other stuff in personal item, my actual roll-aboard carry-on bag just has other stuff in.)