How to run React on Heroku?

Question

Heroku

Writes that it cannot get GET (cannot get /). I already did build and indicated ..

const express = require('express');
const config = require('config');
const mongoose = require('mongoose');
const path = require('path');

const app = express();

app.use(express.json({ extended: true }));

app.use('/api/auth', require('./routes/auth'));
app.use('/api/search', require('./routes/search'));

app.use('/', express.static(path.join(__dirname, 'client/build')));

const PORT = process.env.PORT || 5000;

async function start() {
    try {
        mongoose.connect(config.get('mongoUri'), {
            useNewUrlParser: true,
            useUnifiedTopology: true,
            useCreateIndex: true
        });
        app.listen(PORT, () => console.log(`Running on ${PORT}`));
    } catch(e) {
        console.log('Server Error', e.message);
        process.exit(1);
    }
}

start();