July 2 (Reuters) - Canada’s main stock index opened higher on Friday, boosted by energy and mining stocks, even as official data showed the nation posted a surprise trade deficit in May. * At 9:30 a.m. ET (13:30 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was up 172.87 points, or 0.86%, at 20,338.45. (Reporting by Amal S in Bengaluru; Editing by Rashmi Aich) Our Standards: The Thomson Reuters Trust Principles.