todo

package main

import (
    "fmt"
    "io"
    "os"
    "sort"
)

func main() {
    out := os.Stdout
    if !(len(os.Args) == 2 || len(os.Args) == 3) {
        panic("usage go run main.go . [-f]")
    }
    path := os.Args[1]
    printFiles := len(os.Args) == 3 && os.Args[2] == "-f"
    err := dirTree(out, path, printFiles)
    if err != nil {
        panic(err.Error())
    }
}
func dirTree(out io.Writer, path string, withFiles bool) error {
    return dirTreeLeveled(out, path, withFiles, 0)
}

// todo
func dirTreeLeveled(out io.Writer, path string, withFiles bool, level int) error {
    dir, err := os.Open(path)
    if err != nil {
        return err
    }
    files, err := dir.Readdir(0)
    sort.Slice(files, func(i, j int) bool {
        return files[i].Name() < files[j].Name()
    })
    for i, f := range files {
        if (!withFiles && !f.IsDir()) {
            continue
        }

        for j := 0; j < level; j++ {
            fmt.Print("\t")
        }
        if i == len(files)-1 {
            fmt.Print("└───")
        } else {
            fmt.Print("├───")
        }
        fmt.Printf("%s\n", f.Name())
        if (f.IsDir()) {
            errInner := dirTreeLeveled(out, path+string(os.PathSeparator)+f.Name(), withFiles, level+1)
            if errInner != nil {
                return errInner
            }
        }
    }
    return nil
}