Docs: update Server.RegisterRoutes docs

server.go

@@ -450,7 +450,9 @@ func (s *Server) Start() error {
 	return nil
 }
 
-// RegisterRoutes creates a new Router for this Server and runs the given `routeRegistrer`.
+// RegisterRoutes runs the given `routeRegistrer` function with this Server and its router.
+// The router's regex cache is cleared after the `routeRegistrer` function returns.
+// This method should only be called once.
 func (s *Server) RegisterRoutes(routeRegistrer func(*Server, *Router)) {
 	routeRegistrer(s, s.router)
 	s.router.ClearRegexCache()