How can I keep the crust of my breads from getting too dark?
Foil will reflect heat, and I have a canonical answer on here someplace about using it to modify baking in ovens that have issues with, say, burning the bottom of a loaf.

But if the whole loaf is affected, the problem is one of temperature or ingredients (or the intersection of the two.) Less sugar in the dough will reduce browning of the crust, and lower temperature will also reduce browning of the crust. Assuming you are happy with the overall taste, I'd start with turning the oven down, not attempting to shield the whole loaf with foil. You may need to increase baking time at lower temperature.