def METHOD_NAME(doi):
    """Returns the metadata of an article given its DOI from CrossRef
    as a JSON dict"""
    url = crossref_url + 'works/' + doi
    res = requests.get(url)
    if res.status_code != 200:
        logger.info('Could not get CrossRef metadata for DOI %s, code %d' %
                    (doi, res.status_code))
        return None
    raw_message = res.json()
    metadata = raw_message.get('message')
    return metadata