package main

import (
	"fmt"
	"os"
	"strings"
	"sync"
)

func main() {
	files := findFilesByExt(".", ".zip")

	var wg sync.WaitGroup

	for _, file := range files {
		wg.Add(1)
		go processFile(&file, &wg)
	}
	wg.Wait()
	println("Done processing")
}

func processFile(file *os.FileInfo, wg *sync.WaitGroup) {
	defer wg.Done()
	println("Processing " + (*file).Name())
}

func findFilesByExt(directory string, extension string) []os.FileInfo {
	f, err := os.Open(directory)
	if err != nil {
		fmt.Fprintf(os.Stderr, "could not open directory: %v\n", err)
		return nil
	}
	defer f.Close()

	entries, err := f.Readdir(0)
	if err != nil {
		fmt.Fprintf(os.Stderr, "could not read dir: %v\n", err)
	}

	var found []os.FileInfo
	for _, file := range entries {
		if strings.HasSuffix(file.Name(), extension) && !file.IsDir() {
			found = append(found, file)
		}
	}
	return found
}

Processing file1.zip
Processing file2.zip
Done processing

Processing file2.zip
Processing file2.zip
Done processing