gt.go

// show go module dependencies as an indented tree
// usage: go mod graph | go run gt.go
package main

import (
	"bufio"
	"fmt"
	"os"
	"strings"
)

func show(root string, deps map[string][]string, depth int) {
	fmt.Println(strings.Repeat("\t", depth), root)
	for _, dep := range deps[root] {
		show(dep, deps, depth + 1)
	}
}

func main() {
	root := ""
	deps := make(map[string][]string)

	scanner := bufio.NewScanner(os.Stdin)
	for scanner.Scan() {
		parts := strings.Split(scanner.Text(), " ")
		if len(parts) != 2 {
			continue
		}
		l, r := parts[0], parts[1]
		if root == "" {
			root = l
		}
		if deps[l] == nil {
			deps[l] = make([]string, 0)
		}
		deps[l] = append(deps[l], r)
	}
	show(root, deps, 0)
}