Add hot reload for backend

Signed-off-by: Asai Neko <sugar@sne.moe>

config/types.go

@@ -13,9 +13,9 @@ type config struct {
 type server struct {
 	Application string `yaml:"application"`
 	Address     string `yaml:"address"`
+	ExternalUrl string `yaml:"external_url"`
 	DebugMode   string `yaml:"debug_mode"`
 	FileLogger  string `yaml:"file_logger"`
-	JwtSecret   string `yaml:"jwt_secret"`
 }
 
 type database struct {