diff --git a/include/rest_rpc/router.h b/include/rest_rpc/router.h
index 8f7d268..bd1449c 100644
--- a/include/rest_rpc/router.h
+++ b/include/rest_rpc/router.h
@@ -154,52 +154,40 @@ class router : asio::noncopyable {
     result = msgpack_codec::pack_args_str(result_code::OK, r);
   }
 
-  template <typename Function> struct invoker {
-    static inline void apply(const Function &func,
-                             std::weak_ptr<connection> conn,
-                             nonstd::string_view str, std::string &result) {
+  template <typename Function>
+  void register_nonmember_func(uint32_t key, Function f) {
+    this->map_invokers_[key] = [f](std::weak_ptr<connection> conn,
+                                   nonstd::string_view str,
+                                   std::string &result) {
       using args_tuple = typename function_traits<Function>::bare_tuple_type;
       msgpack_codec codec;
       try {
         auto tp = codec.unpack<args_tuple>(str.data(), str.size());
-        call(func, conn, result, std::move(tp));
+        call(f, conn, result, std::move(tp));
       } catch (std::invalid_argument &e) {
         result = codec.pack_args_str(result_code::FAIL, e.what());
       } catch (const std::exception &e) {
         result = codec.pack_args_str(result_code::FAIL, e.what());
       }
-    }
+    };
+  }
 
-    template <typename Self>
-    static inline void apply_member(const Function &func, Self *self,
-                                    std::weak_ptr<connection> conn,
-                                    nonstd::string_view str,
-                                    std::string &result) {
+  template <typename Function, typename Self>
+  void register_member_func(uint32_t key, const Function &f, Self *self) {
+    this->map_invokers_[key] = [f, self](std::weak_ptr<connection> conn,
+                                         nonstd::string_view str,
+                                         std::string &result) {
       using args_tuple = typename function_traits<Function>::bare_tuple_type;
       msgpack_codec codec;
       try {
         auto tp = codec.unpack<args_tuple>(str.data(), str.size());
-        call_member(func, self, conn, result, std::move(tp));
+        call_member(f, self, conn, result, std::move(tp));
       } catch (std::invalid_argument &e) {
         result = codec.pack_args_str(result_code::FAIL, e.what());
       } catch (const std::exception &e) {
         result = codec.pack_args_str(result_code::FAIL, e.what());
       }
-    }
-  };
-
-  template <typename Function>
-  void register_nonmember_func(uint32_t key, Function f) {
-    this->map_invokers_[key] = {std::bind(
-        &invoker<Function>::apply, std::move(f), std::placeholders::_1,
-        std::placeholders::_2, std::placeholders::_3)};
-  }
-
-  template <typename Function, typename Self>
-  void register_member_func(uint32_t key, const Function &f, Self *self) {
-    this->map_invokers_[key] = {std::bind(
-        &invoker<Function>::template apply_member<Self>, f, self,
-        std::placeholders::_1, std::placeholders::_2, std::placeholders::_3)};
+    };
   }
 
   std::unordered_map<uint32_t,