How do I translate this sample written in go code to C code ?

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C

Go

Currently translating weighted DAG to C code which is written in Go language and topologically sorted. Actually I missed a couple part of the code that is the code below sample. In topoSort function, I couldn't get what "visit" declaration is. Is it function declaration within another function ? Another part is that in main function that you'll see it below, couldn't get slicing processes with range keyword in loops. If you translate into C syntax roughly or briefly that would be great.

// topoSort()

func (g *graph) topoSort() []int {
    result := make([]int, g.size())
    marks := make([]bool, g.size())
    resultIndex := g.size() - 1

    var visit func(int)
    visit = func(u int) {
        for _, item := range g.adjList[u] {
            if !marks[item.vertex] {
                visit(item.vertex)
            }
        }

        marks[u] = true
        result[resultIndex] = u
        resultIndex--
    }

    for u := range g.adjList {
        if !marks[u] {
            visit(u)
        }
    }

    return result
}

// main()

i := 0
	for rowIndex, row := range input {
		for _, number := range row {
			if rowIndex+1 >= len(input) { // Last row.
				g.addEdge(i, vertexesQuantity, number)
			} else { // Not the last row.
				g.addEdge(i, i + rowIndex + 1, number)
				g.addEdge(i, i + rowIndex + 2, number)
			}

			i++
		}
	}

What I have tried:

I made it and converted basic graph ( weighted DAG ) structure from that sample and there no issue about that. I just struggled with that two of them functions to convert to C code as I described above.