Streaming combine zips

zips.go

package main

import (
	"archive/zip"
	"io"
	"net/http"
	"path/filepath"
)

func downloadZips(w io.Writer) error {
	zwrite := zip.NewWriter(w)
	defer zwrite.Close()

	zipFiles, err := filepath.Glob("archive*.zip")
	if err != nil {
		return err
	}

	for _, zipFile := range zipFiles {
		zipReader, err := zip.OpenReader(zipFile)
		if err != nil {
			return err
		}
		defer zipReader.Close()

		for _, file := range zipReader.File {
			f, err := file.Open()
			if err != nil {
				return err
			}
			defer f.Close()

			fw, err := zwrite.Create(file.Name)
			if err != nil {
				return err
			}

			_, err = io.Copy(fw, f)
			if err != nil {
				return err
			}
		}
	}

	return nil
}

func main() {
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/zip")
		w.Header().Set("Content-Disposition", "attachment; filename=artifact.zip")

		err := downloadZips(w)
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
		}
	})

	http.ListenAndServe("localhost:8080", nil)
}