What are the requirements for admissions to a masters degree in computer science in Canada for an international student? I am a double major in Physics and Computer Science from an underdeveloped country. I would like to apply for a masters in computer science in Canada. What requirements do you think I should fulfill?

Currently, I have a CGPA of 4.0 (and I have only four additional semesters to go), although that CGPA is likely to go down by a small margin over time.
You should check the minimum requirements of the program you are aiming to apply.

But, generally speaking; you may need some proof of language skills (depending on whether your language of study in your BS was English or you are native English speaking, you may not need this document) and official report of your grades and GPA.

Some universities may need a statement of purpose and depending on the entry requirements, you may have to sit an entrance exam or an oral interview via internet. Some universities may require a report of GRE score which you should prepare for separately.

Also you need to find a way to pay your tuition fees and living costs. If you are not self-funding, it is a good idea to check the scholarships which you are eligible for (some of these scholarships are reported on the website of the departments and universities).