That's what the nice little can of doggie mace on your belt that you bought from a postal supply company is for...oh ? you don't have any ? - GET some.
No offense to the canine crowd, and I've pity on the doggie, but when it comes to it...you know.
Letting a dog run loose is a bad idea anyhow, it's not good for the neighborhood, and it's not very good or safe for the doggie, either.
I have had an owner pitch a violent fit about me daring to prevent his mongrel from mauling my leg and hauling me off the ped at a stop sign once, as if I should have just let the critter mangle me, ugh...found out that doggie mace works pretty good on people too...oops...was that your face ? sorry bout that.
Nowadays I just stop and stick that metal pegleg of mine out there, let em get a mouthfulla THAT...heh, and they never try biting me again, that's fer sure.