prefer rwmutex, add parallel benchmark

router.go

@@ -146,7 +146,7 @@ func (app *App) nextCustom(c CustomCtx) (bool, error) { //nolint: unparam // boo
 }
 
 func (app *App) next(c *DefaultCtx) (bool, error) {
-	app.mutex.Lock()
+	app.mutex.RLock()
 
 	// Get stack length
 	tree, ok := app.treeStack[c.methodINT][c.treePath]
@@ -154,7 +154,7 @@ func (app *App) next(c *DefaultCtx) (bool, error) {
 		tree = app.treeStack[c.methodINT][""]
 	}
 	lenTree := len(tree) - 1
-	app.mutex.Unlock()
+	app.mutex.RUnlock()
 
 	// Loop over the route stack starting from previous index
 	for c.indexRoute < lenTree {
@@ -381,7 +381,7 @@ func (app *App) addRoute(method string, route *Route, isMounted ...bool) {
 	app.mutex.Lock()
 	defer app.mutex.Unlock()
 
-	fmt.Printf("addRoute: method: %s, route: %v, isMounted: %v\n", method, route, isMounted)
+	//fmt.Printf("addRoute: method: %s, route: %v, isMounted: %v\n", method, route, isMounted)
 
 	// Check mounted routes
 	var mounted bool

router_test.go

@@ -595,6 +595,34 @@ func Benchmark_Router_Next(b *testing.B) {
 	require.Equal(b, 4, c.indexRoute)
 }
 
+func Benchmark_Router_Next_Parallel(b *testing.B) {
+	app := New()
+	registerDummyRoutes(app)
+	app.startupProcess()
+
+	request := &fasthttp.RequestCtx{}
+
+	request.Request.Header.SetMethod("DELETE")
+	request.URI().SetPath("/user/keys/1337")
+	var res bool
+	var err error
+
+	c := app.AcquireCtx(request).(*DefaultCtx) //nolint:errcheck, forcetypeassert // not needed
+
+	b.ResetTimer()
+
+	b.RunParallel(func(p *testing.PB) {
+		for p.Next() {
+			c.indexRoute = -1
+			res, err = app.next(c)
+		}
+	})
+
+	require.NoError(b, err)
+	require.True(b, res)
+	require.Equal(b, 4, c.indexRoute)
+}
+
 // go test -v ./... -run=^$ -bench=Benchmark_Route_Match -benchmem -count=4
 func Benchmark_Route_Match(b *testing.B) {
 	var match bool