code: func (b *Board) String() string {
  	fen := ""
  	for r := 7; r >= 0; r-- {
  		for f := 0; f < numOfSquaresInRow; f++ {
  			sq := getSquare(File(f), Rank(r))
  			p := b.Piece(sq)
  			if p != NoPiece {
  				fen += p.getFENChar()
  			} else {
  				fen += "1"
  			}
  		}
  		if r != 0 {
  			fen += "/"
  		}
  	}
  	for i := 8; i > 1; i-- {
  		repeatStr := strings.Repeat("1", i)
  		countStr := strconv.Itoa(i)
  		fen = strings.Replace(fen, repeatStr, countStr, -1)
  	}
  	return fen
  }
docs: // String implements the fmt.Stringer interface and returns
  // a string in the FEN board format: rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR