I'm really sorry to hear man. A couple years ago (I was freshly 20) my German Shepherd passed of bone marrow cancer. Love that dog with all of my heart. One of the smartest and kindest, but believe me, he whooped some behind in his prime) dogs I've ever known. It was heartbreaking, really messed me up for a little while. I grew up with that pup. We ended up getting lucky at the Animal Hospital that wasn't our normal vet (we found out about the cancer less than 12 hours before he died, it was an extremely progressive case combined with pancreus problems) and they let us take him home while he was still barely there and gave us an extra sedative incase he lived until morning and we could bring him to our local Vet to get put down.
Before anyone says thats horrible we didn't just put him down right away, just keep your opinion to yourself. He was on plenty of pain meds, and we had some incase he made it through the night, which we were assured he wouldn't, and he didn't. We brought him home because the Animal Hospital said they legally would have to cremate him if they put him down, adn my dad and I both agreed we would bury the 130lb beast at home, in his own backyard, his castle. There is no worse feeling than having to say goodbye while they lay there and stare at you, but don't have the power to move or even lick your face one last time. Sure enough, at 6 am the next morning my dad, younger brother and I burried him, hand dug the grave as the sun rose.
Now I'm all teary eyed.
I feel for your loss. Man. Many many vibes your way.