Select "Saute" on the pressure cooker and add the coconut oil.
Add the diced onion and saute until translucent.
Add the minced garlic and saute for about a minute more.
Add the mushrooms, salt and pepper. Continue to saute until onions are lightly browned and mushrooms begin to get some color.
Add about 1/2 cup of water or preferred broth and stir up any browned bits from the bottom of the pot. Let simmer for 1-2 minutes.
Add the rice, remaining 2 1/2 cups of water, lemon juice and pepper.
Turn off the "Saute" function and set the pressure cooker manually to 22 minutes or follow your pressure cooker's instructions for brown rice. Most require longer than the "Rice" setting allows.
Allow the pressure to release naturally for at least 10 minutes before doing a quick release. I think it's best to let it naturally release completely if you have the time.
Fluff rice and serve.