If you do it, it is all over. Really over, not like a restart in a game. Youre on a planet in the middle of the universe and you have been given a consciousness to experience taste and sound and sight... I dunno, to me it seems like a waste to throw it away. Death comes too soon as it is.
Life is so ful of possibilities. You say you have no kids, no friends... I had friends and I lost friends, I found new ones or rekindled our lost friendships. For a few years I was in a totally shitty place because of drugs, underweight, no gf, no one close to me, lost all my friends and money, nothing to really live for. But once you see what is happening, what you are doing wrong and try changing things, it does happen. There are so many things to miss if you stop your existence.
You can still have kids, find a partner, adopt kids since there are thousands without parents living shitty lifes in orphanages. Life is freedom. You feel like you are stuck and right now see things one way. But reality is not like that. There is no one way to see things. Try to stop painting a picture in your head how terrible everything is. It is really not, its our actions that lead us to where we are, and actions come from our thoughts and ideas. Try to change your way of thinking a bit. I am telling you can, no prob. We have all been at some point of our lifes in a messed up place. Lonely, lost, confused. But killing yourself is so not a good idea. Really really think about it. Dont you want to find a nice partner and love, experience things together, travel or whatever, or just simple things, good food, a good movie, a fresh warm sunny morning. Jogging and then a shower and a pizza. Move to a different continent if you think that is what it takes. As cliche as it might sound, listen to your heart, your gut feeling.
You are suffering now but please do not do it. And you are not suffering physically but it is your mind. You have told yourself so many times how awful everything is. But it really is not. And it takes willpower but at least try to change you life a bit towards what you want it to be. Do not say you already tried. You say you have been in a funk for years. Think about it, really think about it. Meditate if that is what it takes and try to see what you expect of life and what you did wrong during these years. You can always kill yourself.
There is so much to experience, please do not go through with it, give it time and make some changes. And do report back.