add Module.RequireLoaded helper

module.go

@@ -54,3 +54,10 @@ func (s *Module) Name() string {
 func (s *Module) Loaded() bool {
 	return s.loaded
 }
+
+// RequireLoaded panics if the module is not loaded.
+func (s *Module) RequireLoaded() {
+	if s == nil || !s.Loaded() {
+		panic(fmt.Sprintf("module %s not loaded", s.name))
+	}
+}