Losing currentUser when App component refreshes? - node.js

Question

I am currently working on a simple web app using React, Node.js, passport-google-oauth20.
For some reason, whenever the application re-mounts, I lose the currentUser state. It's as if req.user is just lost.
The way it works is I first fetch the current user when the application mounts and set this.state.currentUser to the results. The issue is when the page refreshes. The component re-mounts and I lose the user. I tried logging the user and receive null.
Hopefully I explained this well enough... here is the code:
App component:
import React from 'react';
import List from './List';
import ListForm from './ListForm';
import * as helpers from '../helpers';
class App extends React.Component{
state = {
currentUser: '',
}
componentDidMount() {
helpers.fetchUser()
.then(data => {
this.setState({
currentUser: data
});
});
}
onSubmit = (id, item) => {
helpers.addItem(id, item);
}
render() {
return (
<div className="container">
<List
currentUser={this.state.currentUser}
onSubmit={this.onSubmit}
/>
</div>
);
}
};
export default App;
Helpers:
import axios from 'axios';
export const fetchUser = async () => {
const resp = await axios.get('/api/current_user');
return resp.data;
}
export const addItem = (id, newItem) => {
axios.post("/api/" + id + "/addItem", newItem);
}