text: const localTunnel = require('localtunnel')
  
  
  let tunnel = localTunnel(4000, (err, tunnel) => {
      if (err)
          console.log('tunnel err', err)
  
      const fs = require('fs');
      fs.writeFileSync('tunnel.json', JSON.stringify({ serverURL: tunnel.url }), {flag : 'w'})
      tunnel.on('close', () => { console.log('tunnel closed') })
      tunnel.on('error', (err) => { console.log('tunnel error = ', err) })
      console.log('tunnel run success')
  }) 