package main

import (
    "fmt"
    "os"
    "path/filepath"
    "flag"
    "strings"
)

var (
        EXT       string             = "txt"
)

func main() {

    flag.StringVar(&EXT, "e", EXT, "")
    flag.Parse()
    fmt.Println("Extension:", EXT)

    curdirname := ""
    flg := false

    filepath.Walk(".", func(path string, info os.FileInfo, err error) error {
    if info.IsDir() {
        if flg {
                fmt.Println(curdirname)
            flg = false
        }
        curdirname = path

    } else {
        if strings.Contains(path,"."+EXT) {
            flg = true
        }
    }

        return nil
    })
}