第三国签证预约的问题，canada

I was trying to make the appointment to the consulte in Vancouver. But the system told me that I can only do it 8 week in front. The problem is there even no appointment avaiable now which means all are booked for next 8 weeks. So I think it may be very hard to get an appointment. I am worrying about it as I am going to Canada for landing in June. Any suggestions for how to make the appointment? Thanks a lot.