I went to Toronto during the Spring Festival to visit my boyfriend who is studying there, staying for twenty days. What should I say to the customs officer when I enter the country?

I am going to Canada alone to find my boyfriend, who is studying. I have a job in my home country and I want to stay in Canada for twenty days. I have already purchased the round-trip ticket. Should I truthfully tell the customs that I am going to find my boyfriend, or say that I am going for a vacation? However, if they ask for my address of residence, I definitely have to say that I will be staying at my boyfriend’s house. I am afraid that if I stay too long, the customs may not agree and decide to deport me.