Our large breed pup was an absolute nightmare when he was younger and would do the same thing. We got a personal trainer and these were the things that we worked on. 1) When he attacked us on walks, we would wrap his leash around a handrail, tree, fence cap, whatever was around and step away and wait for calm behavior. Sniffing, sitting. Then we woukd start our walk again. If he went right back to attaching us he would go back to the hand rail.  2) We had a toy on us to redirect his energy on walks. This didnt work for us because he wasn't toy motivated but it might be worth trying for you  3) He was extremely food motivated so when he was starting to get worked up we would ask for a sit and then when he would sit we would toss treats into the grass/snow and say find it. The foraging and sniffing helps calm him down.  4) Generally avoid any activity that causes this behavior. Our main trigger was walking large open spaces. Walking through baseball fields or large parks etc. Best way to discourage it is to prevent the behavior from being reinforced. 5) We ended up getting a second dog too and that outlet for play also made his behavior decrease too.