go example that shows how to walk a directory using a regular expression filter and collect files that match

walker.go

// This example demonstrates how to use go to walk a directory
// and filter the contents by using filepath.Walk with
// variables in the external scope to provide the filter and
// to capture the file names.
//
// To build:
//     go build walk.go
// Usage:
//     walk <pattern> <files>
//
// License:
//     MIT Open Source
//     Copyright (c) 2016 by Joe Linoff
package main

import (
	"fmt"
	"os"
	"path/filepath"
	"regexp"
)

func main() {
	if len(os.Args) > 1 {
		re := regexp.MustCompile(os.Args[1]);
		for i := 2 ; i < len(os.Args); i++ {
			filteredSearchOfDirectoryTree(re, os.Args[i])
		}
	}
}

// filteredSearchOfDirectoryTree Walks down a directory tree looking for
// files that match the pattern: re. If a file is found print it out and
// add it to the files list for later user.
func filteredSearchOfDirectoryTree(re *regexp.Regexp, dir string) error {
	// Just a demo, this is how we capture the files that match
	// the pattern.
	files := []string{}
	
	// Function variable that can be used to filter
	// files based on the pattern.
	// Note that it uses re internally to filter.
	// Also note that it populates the files variable with
	// the files that matches the pattern.
	walk := func(fn string, fi os.FileInfo, err error) error {
		if re.MatchString(fn) == false {
			return nil
		}
		if fi.IsDir() {
			fmt.Println(fn + string(os.PathSeparator))
		} else {
			fmt.Println(fn)
			files = append(files, fn)
		}
		return nil
	}
	filepath.Walk(dir, walk)
	fmt.Printf("Found %[1]d files.\n", len(files))
	return nil
}

Thanks