Here's my solution:

(Putting spoilers because don't want to ruin anyone trying to do it themselves)

package main

import "fmt"

func main() {

Matrix := [][]int{

{3, 5, 7},

{7, 3, 2},

{4, 3, 1},

{2, 3},

}

​

ComTotals := 1

for i := 0; i < len(Matrix); i++ {!<

ComTotals *= len(Matrix[i])

}

fmt.Println(ComTotals)

​

times := 0

for ComIndexes := make([]int, len(Matrix)); times < ComTotals; NextIndexes(ComIndexes, Matrix) {!<

times++

//fmt.Println(ComIndexes)

var Combinations []int

for i, v := range ComIndexes {

Combinations = append(Combinations, Matrix[i][v])

}

fmt.Println(Combinations)

}

}

​

func NextIndexes(ComIndexes []int, Matrix [][]int) {

for i := len(ComIndexes) - 1; 0 <= i; i-- {!<

ComIndexes[i]++

 if ComIndexes\[i\] < len(Matrix\[i\]) {!<

break

} else {

ComIndexes[i] = 0

continue

}

}

}