Provide runtime environment to app made with create-react-app

App.js

import React, { Component } from "react";
import Navigation from "./Navigation";
import withConfig from "./withConfig";

class App extends Component {

  componentWillMount() {
     console.log(this.props.config);
  }

 render() {
  const {config} = this.props;
  return <Navigation someVar={config.SOME_VAR} />
 }
}
export default withConfig(App);

package.json

{
  "name": "myapp",
  "version": "1.0.0",
   "author": "Julian Mann",
  "dependencies": {
    "express": "^4.15.3",
    "react": "^15.6.1",
    "react-addons-css-transition-group": "^15.6.0",
    "react-dom": "^15.6.1"
  },
  "devDependencies": {
    "ava": "^0.20.0",
    "proxyquire": "^1.8.0",
    "react-scripts": "1.0.7"
  },
  "scripts": {
    "start": "node server.js",
    "dev": "PORT=8080 react-scripts start",
    "build": "react-scripts build"
  },
  "engines": {
    "node": ">=4.3.2"
  },
  "proxy": "http://localhost:5000"
}

server.js

const express = require("express");
const path = require("path");
const app = express();

var config = {
	API_URL: process.env.API_URL || "http://api.somesite.com",
	SOME_VAR: process.env.SOME_VAR || "some-value"
};

app.use(express.static(path.join(__dirname, "build")));

app.get("/config", function(req, res) {
	res.json(config);
});

app.get("*", (req, res) => {
	res.sendFile(path.join(__dirname, "build", "index.html"));
});

let server = app.listen(process.env.PORT || "5000", () => {
	console.log("App listening on port %s", server.address().port);
	console.log("Press Ctrl+C to quit.");
});

withConfig.js

import React, { Component } from "react";

function withConfig(WrappedComponent) {

  return class extends Component {
    constructor(props) {
      super(props);
      this.state = {};

      fetch("/config")
        .then(res => res.json())
        .then(data => {
           this.state = data;
        })
        .catch(function() {
          console.log("Cant reach server");
        });
    }
    render() {
      return <WrappedComponent {...this.props} config={this.state} />;
    }
  };

}

export default withConfig;