just use executor() for what get_executor() was doing

include/appbase/application_base.hpp

@@ -352,19 +352,19 @@ class application_t : public application_base {
     */
    template <typename Func>
    auto post(int priority, Func&& func) {
-      return get_executor().post(priority, std::forward<Func>(func));
+      return executor().post(priority, std::forward<Func>(func));
    }
 
    /**
     *  Wait until quit(), SIGINT or SIGTERM and then shutdown.
     *  Should only be executed from one thread.
     */
    void exec() {
-      application_base::exec(get_executor());
+      application_base::exec(executor());
    }
 
    boost::asio::io_service& get_io_service() {
-      return get_executor().get_io_service();
+      return executor().get_io_service();
    }
 
    void startup() {
@@ -373,19 +373,15 @@ class application_t : public application_base {
 
    application_t() : application_base(std::make_shared<executor_t>()) {
       set_stop_executor_cb([&]() { get_io_service().stop(); });
-      set_post_cb([&](int prio, std::function<void()> cb) { get_executor().post(prio, std::move(cb)); });
+      set_post_cb([&](int prio, std::function<void()> cb) { executor().post(prio, std::move(cb)); });
    }
 
-   executor_t& executor() {
-      return get_executor();
+   executor_t& executor() const {
+      return *static_cast<executor_t*>(executor_ptr.get());
    }
 
 private:
    inline static std::unique_ptr<application_t> app_instance;
-
-   executor_t& get_executor() const {
-      return *static_cast<executor_t*>(executor_ptr.get());
-   }
 };