code: func (d Driver) Land() {
  	d.mutex.Lock()
  	d.cmd[9] = 0x80
  	d.cmd[10] = checksum(d.cmd)
  	d.mutex.Unlock()
  	time.Sleep(500 * time.Millisecond)
  	d.mutex.Lock()
  	d.cmd[9] = 0x04
  	d.cmd[10] = checksum(d.cmd)
  	d.mutex.Unlock()
  }
docs: // Land tells drone to come in for landing.