old_contents: import express from 'express'
  
  const app = express()
  
  app.use(express.static('client/build'))
  
  app.get('/api/hello', (req, resp) => {
    console.log('hello')
    resp.send('hello')
  })
  
  const port = process.env.PORT || 3001
  app.listen(port, () => {
    console.log(`Listening at http://localhost:${port}`)
  })
  
new_contents: import express from 'express'
  
  const app = express()
  
  app.use(express.static('client/build'))
  
  //TODO use a database...
  const cash = {
    123: {
      items: {
        500: {
          facial: 500,
          count: 2
        },
        200: {
          facial: 200,
          count: 3
        },
      }
    }
  }
  
  app.get('/api/cash/:id', (req, res) => {
    const csh = cash[req.params.id]
    if (csh === undefined) {
      res.status(400).send('Not found')
    }
    res.json(csh)
  })
  
  const port = process.env.PORT || 3001
  app.listen(port, () => {
    console.log(`Listening at http://localhost:${port}`)
  })
  
subject: add GET /api/cash/:id