don't fire ErrServerClosed on manually interrupt signals (CTRL/CMD+C)

Former-commit-id: 673c84dd13bb99c0926aa1b4a6b4eff9745403d8

_examples/miscellaneous/file-logger/main.go

@@ -42,7 +42,7 @@ func main() {
 
 	// Navigate to http://localhost:8080/ping
 	// and open the ./logs{TODAY}.txt file.
-	if err := app.Listen(":8080", iris.WithoutBanner, iris.WithoutServerError(iris.ErrServerClosed)); err != nil {
+	if err := app.Listen(":8080", iris.WithoutBanner); err != nil {
 		app.Logger().Warn("Shutdown with error: " + err.Error())
 	}
 }