func lookupMode(mode string, r *maps.DirectionsRequest) { switch mode { case "driving": r.Mode = maps.TravelModeDriving case "walking": r.Mode = maps.TravelModeWalking case "bicycling": r.Mode = maps.TravelModeBicycling case "transit": r.Mode = maps.TravelModeTransit case "": // ignore default: log.Fatalf("Unknown mode '%s'", mode) } }