code: func (d *Disco) DiscoverServiceURL(hostname svchost.Hostname, serviceID string) (*url.URL, error) {
  	host, err := d.Discover(hostname)
  	if err != nil {
  		return nil, err
  	}
  	return host.ServiceURL(serviceID)
  }
docs: // DiscoverServiceURL is a convenience wrapper for discovery on a given
  // hostname and then looking up a particular service in the result.