List all packages in a Go module

packagestats.go

package main

import (
	"fmt"
	"io/fs"
	"log"
	"os"
	"path/filepath"
	"sort"
	"strings"
)

func run(root string) error {
	var packages []string

	err := fs.WalkDir(os.DirFS(root), ".", func(path string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}

		if !d.IsDir() {
			return nil
		}

		parts := strings.Split(path, string(filepath.Separator))
		if len(parts) < 1 {
			return nil
		}
		// packageName := parts[len(parts)-1]

		for _, part := range parts {
			switch part {
			case "internal", "testdata", "test", "vendor":
				return filepath.SkipDir
			}
		}

		sourceFiles, err := fs.Glob(os.DirFS(filepath.Join(root, path)), "*.go")
		if err != nil {
			return err
		}
		if len(sourceFiles) < 1 {
			return nil
		}

		for _, sourceFile := range sourceFiles {
			if strings.Contains("_test", sourceFile) {
				return nil
			}
		}
		packages = append(packages, path)

		return nil
	})

	sort.Strings(packages)
	for _, packageName := range packages {
		fmt.Println(packageName)
	}

	return err
}

func main() {
	err := run(os.Args[1])
	if err != nil {
		log.Fatal(err)
	}
}