code: func (s *ChainService) GetBlockHash(height int64) (*chainhash.Hash, error) {
  	header, err := s.BlockHeaders.FetchHeaderByHeight(uint32(height))
  	if err != nil {
  		return nil, err
  	}
  	hash := header.BlockHash()
  	return &hash, err
  }
docs: // GetBlockHash returns the block hash at the given height.