unzip a zip file

func unzip(src, dest string) error {
  r, err := zip.OpenReader(src)
  if err != nil {
    return err
  }
  defer r.Close()

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

    path := filepath.Join(dest, f.Name)
    if f.FileInfo().IsDir() {
      os.MkdirAll(path, f.Mode())
    } else {
      f, err := os.OpenFile(
        path, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, f.Mode())
      if err != nil {
        return err
      }
      defer f.Close()

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