When you leave the company you get Relieving letter and not Reference Letter.
Reference and Relieving letter has a difference my friend.
Even if you hide this from your company CHC will inquiry about your employment with your company.
So its better to inform your company before CHC does.
If before you ask for that I m sure you are going to create doubt in
your boss mind that ur planning to leave company.
For this i would tell you that no1 keeps on working for a single company.
Every1 will leave after some time working for a company.
So your boss will understand if he is a professional person. So its upto you to take this challenge and explain him properly that....Boss i am applying for Canadian Visa and the Visa process will take arnd 2+ years of time. So i need the reference Letter as the Canadian embassy needs it for my work proof.
Please provide this.
Just say this to him and he should agree i suppose.
And my advice to you would be to inform about your process and do not hide anything unless you think that informing them might create adverse effects on your job.
Rest its upto you how you handle the situation.
Good Luck