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

Former-commit-id: 673c84dd13bb99c0926aa1b4a6b4eff9745403d8

_examples/http_request/request-logger/main.go

@@ -61,5 +61,5 @@ func main() {
 	// http://localhost:8080/2
 	// http://lcoalhost:8080/notfoundhere
 	// see the output on the console.
-	app.Listen(":8080", iris.WithoutServerError(iris.ErrServerClosed))
+	app.Listen(":8080")
 }