code: func (m *Manager) GetRegistryEntry(username string, globalid string, key string) (registryEntry *RegistryEntry, err error) {
  	selector, err := createSelector(username, globalid, key)
  	result := struct {
  		Entries []RegistryEntry
  	}{}
  	err = m.getRegistryCollection().Find(selector).Select(bson.M{"entries.$": 1}).One(&result)
  	if err == mgo.ErrNotFound {
  		err = nil
  		return
  	}
  	if result.Entries != nil && len(result.Entries) > 0 {
  		registryEntry = &result.Entries[0]
  	}
  	return
  
  }
docs: // GetRegistryEntry gets a registryentry for a user or organization
  // If no such entry exists, nil is returned, both for the registryEntry and error