Chessboard CountInRank Failing Assertions

Exercism
1

I’m working on the Chessboard exercise, and I’ve gotten all the methods working except for CountInRank.

// CountInRank returns how many squares are occupied in the chessboard,
// within the given rank.
func CountInRank(cb Chessboard, rank int) int {
	var num_occupied int = 0
    if rank < 1 || rank > 8 {
        return 0
    } else {
    	for i, _ := range cb {
            if cb[i][rank] == true {
                num_occupied += 1
            }
        }
        return num_occupied
    }
}

This seems to me like it should hit all the files of the rank, and it seems to, but the returned counts are not matching the expected results.

2

Would this solution work to count, say, the first/left most rank?

3

I don’t see why it wouldn’t; I am only allowing ranks between 1 and 8 to be calculated through iteration, per the test case instructions.

4

What index gives the first rank?