code: func (q *QueryDsl) FunctionScore(mode string, functions ...map[string]interface{}) *QueryDsl {
  	q.QueryEmbed.FunctionScore = map[string]interface{}{
  		"functions":  functions,
  		"score_mode": mode,
  	}
  	return q
  }
docs: // FunctionScore sets functions to use to score the documents.
  // http://www.elastic.co/guide/en/elasticsearch/reference/1.x/query-dsl-function-score-query.html