The most important things are already told, but two minor things could be add: You should have Aard ready if the golems does come close to you. Although it won't be the solution, it will at least slow him down, and, in the best case, drive him back a bit. Yrden, if you already have that sign and some talents to spend on it, might also help, as it reduces his hits points a bit, so the pylons might finish him faster. Just get some distance between him and you (best if you have the pylons between him and youafter the follwing step), and cast the sign. then walk back slowly, so he will take the direct path (down arrow) and let him run into the trap. If you time it right, you will also have the time to complete the activation phase for the lightning.