Set modules.

src/utils/Portal.js

@@ -7,7 +7,7 @@
 
 import ReactDOM from 'react-dom';
 
-export default function Portal({containerId, children}) {
+export function Portal({containerId, children}) {
     const container = document.getElementById(containerId);
     if (container)
         return ReactDOM.createPortal(children, container);

src/utils/index.js

@@ -1,3 +0,0 @@
-import Portal from './Portal';
-
-export {Portal}