code: func (d *Driver) GetURL() (string, error) {
  	if err := drivers.MustBeRunning(d); err != nil {
  		return "", err
  	}
  
  	// NOTE (ahmetalpbalkan) I noticed that this is not used until machine is
  	// actually created and provisioned. By then GetIP() should be returning
  	// a non-empty IP address as the VM is already allocated and connected to.
  	ip, err := d.GetIP()
  	if err != nil {
  		return "", err
  	}
  	u := (&url.URL{
  		Scheme: "tcp",
  		Host:   net.JoinHostPort(ip, fmt.Sprintf("%d", d.DockerPort)),
  	}).String()
  	log.Debugf("Machine URL is resolved to: %s", u)
  	return u, nil
  }
docs: // GetURL returns a socket address to connect to Docker engine of the machine
  // instance.