Question: when did season 8 of the walking dead end
[{'answer': 'April 15 , 2018', 'provenance': [{'wikipedia_id': '49550011', 'title': 'The Walking Dead (season 8)', 'start_paragraph_id': 1, 'start_character': 151, 'end_paragraph_id': 1, 'end_character': 166, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]