add missing deleteflash method

forms.go

@@ -101,10 +101,10 @@ func (f FormValue) IsEmpty() bool {
 // GetFormArray gets multiple form values as string slice
 func (ctx Ctx) GetFormArray(key string) []string {
 	var values []string
-	ctx.PostArgs().VisitAll(func(k, v []byte) {
+	for k, v := range ctx.PostArgs().All() {
 		if string(k) == key {
 			values = append(values, string(v))
 		}
-	})
+	}
 	return values
 }

session.go

@@ -104,6 +104,10 @@ func (s *Session) GetFlash(key string) (any, bool) {
 	return value, exists
 }
 
+func (s *Session) DeleteFlash(key string) {
+	s.Delete("flash_" + key)
+}
+
 func (s *Session) GetFlashMessage(key string) string {
 	if flash, exists := s.GetFlash(key); exists {
 		if msg, ok := flash.(string); ok {