code: func (c *xmppClient) Subscribe() error {
  	barejid := c.jid
  	i := strings.Index(barejid, "/")
  	if i >= 0 {
  		barejid = barejid[:i]
  	}
  	println("\nok\n", "jid", c.jid, "\n")
  	fmt.Fprintf(c.tls, "<iq type='set' id='z1'><session xmlns='urn:ietf:params:xml:ns:xmpp-session'/></iq>")
  	fmt.Fprintf(c.tls, "<iq type='set' to='%s' id='z2'><subscribe xmlns='google:push'><item channel='cloudprint.google.com' from='cloudprint.google.com'/></subscribe></iq>", barejid)
  	return nil
  }
docs: // Subscribe sends a subscription request.