Upvote:1
In the case that you want to visit a friend in Nigeria, you can just apply for a visitor visa as on this page of OIS Services, the agency that deals with the applications on behalf of Nigerian embassies:
Apply for a Tourist Visa if you are traveling to Nigeria to explore the country without an invitation letter.
Apply for a Visitor Visa if you are traveling to Nigeria to visit someone who you know and who has provided you with an invitation letter along with a copy of their passport.
In my recent experience (traveling last month from Italy) a letter from me to the embassy and an invitation letter from my Nigerian friend to the embassy (consistent to each other) were enough to apply. Unfortunately I have no idea if different conditions apply to Canadian travelers (as in the tags). Anyway I now see from their website linked above that Canada is one of the locations where you can find OIS Services in the world.