storage/fanout.go
func (q *mergeQuerier) Close() error {
	// TODO return multiple errors?
	var lastErr error
	for _, querier := range q.queriers {
		if err := querier.Close(); err != nil {
			lastErr = err
		}
	}
	return lastErr
}
func (q *mergeQuerier) Close() error {
	// TODO return multiple errors?
	var lastErr error
	for _, querier := range q.queriers {
		if err := querier.Close(); err != nil {
			lastErr = err
		}
	}
	return lastErr
}
// Close releases the resources of the Querier.