docs: function loadCallback () {
    io.loadText('assets/hello.txt', (err, text) => {
      if (err) return console.log(err)
      state.callback.text = text
    })
  
    io.loadJSON('assets/color.json', (err, json) => {
      if (err) return console.log(err)
      state.callback.json = json
    })
  
    io.loadImage('assets/pex.png', (err, image) => {
      if (err) return console.log(err)
      state.callback.image = image
    })
  
    io.loadBinary('assets/data.bin', (err, data) => {
      if (err) return console.log(err)
      state.callback.binary = data
    })
  }