I thought the Go code looked way too complex and Python would be simpler. Yes and no.

  import csv
  
  filename = 'example.csv'
  sort_by = 'index'
  reverse = True
  
  with open(filename) as f:
      lines = [d for d in csv.DictReader(f)]
  
  for line in lines:
      line['index'] = int(line['index'])
  lines.sort(key=lambda line: line[sort_by], reverse=reverse)
  print(','.join(lines[0].keys()))
  for line in lines:
      print(','.join(str(v) for v in line.values()))