I feel for you, and understand your deep pain. Prayers sent. Over quite a few years, I've had to have a number of faithful dogs euthanized, and in the case of three of them, I had to do it by myself, mercifully and quickly with a .22. Nothing in my life has ever been harder for me to do. I know without a doubt that I've cried over more dogs than people. They are by and large selfless, loving and loyal - more than I can say for most humans. When it's their time and when they pass, it's heart-wrenching, for sure. May you meet again on the other side of the Rainbow Bridge. If dogs don't go to heaven, I'm not sure it would be heaven.
John