Yes, I remember reading it and it really hit me back when I was a kiddo. I think the dog sensed death, moved on and we realized the gravity of the situation.
I did a quick look around the internets, and I see there is another version with a happy ending. I don’t know which one is best; I would have forgotten the happier one a lot, lot sooner.
Another Jack London short story I highly recommend is “The Law of Life.” Easily found on the web.
By the way, his Wikipedia biography is amazing. It was a lot more difficult to travel back then. He went everywhere, lived hard, and died young.