Implement option to disable automatic NotFoundHandler registration

README.md

@@ -152,6 +152,13 @@ mux.HandleFunc("/hello", routegroup.Wrap(helloHandler, loggingMiddleware, corsMi
 http.ListenAndServe(":8080", mux)
 ```
 
+### Automatic registration of `NotFoundHandler` as catch-all route
+
+`routegroup` automatically registers a `NotFoundHandler` as a catch-all route, which is invoked when no other route matches the request. This handler is wrapped with all the middlewares that are associated with the group. This functionality is beneficial for applying middleware to all routes, including those that are unknown. It practically enables the use of middlewares that should operate across all routes, such as logging.
+
+In case you want to disable this behavior, you can use the `DisableNotFoundHandler()` function.
+
+
 ## Real-world example
 
 Here's an example of how `routegroup` can be used in a real-world application. The following code snippet is taken from a web service that provides a set of routes for user authentication, session management, and user management. The service also serves static files from the "assets/static" embedded file system.

group.go

@@ -15,8 +15,9 @@ type Bundle struct {
 	basePath    string                            // base path for the group
 	middlewares []func(http.Handler) http.Handler // middlewares stack
 
-	rootRegistered atomic.Value // true if the root path is registered in the mux
-	once           sync.Once    // used to register a not found handler for the root path if no / route is registered
+	rootRegistered             atomic.Value // true if the root path is registered in the mux
+	once                       sync.Once    // used to register a not found handler for the root path if no / route is registered
+	disableRootNotFoundHandler bool         // if true, the not found handler for the root path is not registered automatically
 }
 
 // New creates a new Group.
@@ -36,12 +37,11 @@ func Mount(mux *http.ServeMux, basePath string) *Bundle {
 // ServeHTTP implements the http.Handler interface
 func (b *Bundle) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	b.once.Do(func() {
-		if !b.rootRegistered.Load().(bool) {
+		if !b.rootRegistered.Load().(bool) && !b.disableRootNotFoundHandler {
 			// register a not found handler for the root path if no / route is registered
 			// this is needed to be able to use middleware on all routes, for example logging
 			notFoundHandler := http.NotFoundHandler()
 			b.register("/", notFoundHandler.ServeHTTP)
-			b.rootRegistered.Store(true)
 		}
 	})
 
@@ -109,6 +109,11 @@ func (b *Bundle) Handler(r *http.Request) (h http.Handler, pattern string) {
 	return b.mux.Handler(r)
 }
 
+// DisableNotFoundHandler disables the automatic registration of a not found handler for the root path.
+func (b *Bundle) DisableNotFoundHandler() {
+	b.disableRootNotFoundHandler = true
+}
+
 // Matches non-space characters, spaces, then anything, i.e. "GET /path/to/resource"
 var reGo122 = regexp.MustCompile(`^(\S*)\s+(.*)$`)