Moss In Turfgrass

Moss is an opportunistic organism/plant in our mild and wet NW region. When you have a combination of shade, acidic soil (which we ALL have), poor drainage, compacted soil, excessive or improper irrigation, low soil fertility or some combination of these, these conditions highly favorable moss growth in turfgrass.
Moss in the lawn is NOT a moss problem, it is a soil and drainage problem. Correct those issues and you can manage the moss growth.
Lawn grass is VERY difficult to grow in too much shade, so first assess if you have enough light (minimum 6-8 hours of open and direct light) for growing grass in that particular area, if not, try growing something else. If it is partial shade, you can use a more shade tolerant grass seed mix.