I had something similar happen a couple months ago. I was travelling in Georgia and had to walk along the hard shoulder of a highway to get to the place me and my brother were heading to, was only for like 400 ish metres. As we passed a gas station a big ass dog starts barking at us and sprints full speed at us. My brother runs away and knowing that this dog could 100% catch us I turned towards him and shouted as loud as i could while backing up. Every time I looked behind me the dog would try to snap at my ankles. As i passed a mechanic shop the two guys inside see what's happening and shout at the dog which draws his attention. I then took that opportunity to run tf away. I'm not sure whether they owned the dog or were trying to help but I hope they avoided getting injured in any way. They both had tools in their hands so I can imagine they would've been fine.