code: func shardEntityID(cn string, total, index int) string {
  	return fmt.Sprintf("%s|%d|%d", cn, total, index)
  }
docs: // shardEntityID returns an ID of CRLShardHeader entity for given shard.
  //
  // 'cn' is Common Name of the CRL. 'total' is total number of shards expected,
  // and 'index' is an index of some particular shard.