Question: when was the last time usa won the gold cup
[{'answer': '2017', 'provenance': [{'wikipedia_id': '250685', 'title': 'CONCACAF Gold Cup', 'start_paragraph_id': 13, 'start_character': 389, 'end_paragraph_id': 13, 'end_character': 393, 'bleu_score': 1.0, 'section': 'Section::::History.:CONCACAF Gold Cup (since 1991).\n'}]}]