Twenty years. It’s been 20 years of heartbreak and folly and mismanagement. Twenty years of bad calls and close calls. Twenty years of team after team and disappointment after disappointment. And now, after all that waiting, the Rangers once again get the opportunity to play for the Stanley Cup. By taking a 1-0 win over the Canadiens in Game 6 of the Eastern Conference finals on Thursday night at the Garden, the Blueshirts took possession of the Prince of Wales Trophy, victors of the conference. Serenaded with a chorus of “We want the Cup” by the Garden crowd, the Rangers now wait to see who comes out of the Kings-Blackhawks series to identify the final roadblock in this quest for the franchise’s second Cup in 74 years. “I don’t think I’ve ever been more determined to win a hockey game,” said Henrik Lundqvist, The King when the Rangers needed him most. The Rangers goalie had to face only 18 shots, but he turned them all away, overtaking Mike Richter on the franchise list with career postseason win No. 42, and tying Richter with postseason shutout No. 9. Of course, Richter is a single link to that iconic squad of 1994, the most recent one that has come this close to the ultimate goal, and one that lives on in the city in perpetuity for bringing home the Cup and ending a 54-year championship drought. It is a place of rarified air, one that would have seemed a pipe dream back when the Rangers were in a tailspin to start the season. “In October?” coach Alain Vigneault said when he was asked what he would have thought had this scenario been given to him back then, when his first year behind the Blueshirts’ bench was looking like a disaster. “I probably would have said, ‘What are you smoking?’ ”