Condolences, man. It sucks. We've lost all 3 of our over the past 5 years. I still talk to the last one daily when I get home from work and she passed in August. No stronger bond than that with a good dog.
Have had two this has happened with, hardest damn thing I ever had to do in my life and I have done some hard things, theres a reason we out live dogs just never figured it out guess its all in the grand scheme of life, think about those buddies every day. Took me three years before I could get another, but he is sitting right beside me now. My condolences.
All dog people know your pain. You can take solace in the fact that with the time your dog was here, that you both got to spend his life with each other and he cherished it just as much as you did.