It is with deep regret that I must inform you of my need to leave XXX（要離職的公司名稱） at the end of this April.
I value this xx year I have spent and the friends I have made. This position has taught me invaluable lessons, and for this I am very grateful. I do feel, however, I have decided to leave XXX （要離職的公司名稱） in order to go to VANCOUVER, Canada to join my family.
Thank you for your continued support and guidance. I hope my departure does not place too much of an inconvenience. I will be happy to do whatever I can to make this transition as easy as possible.