Safari在提取时将zip文件下载为“未知”（使用polyfill）

I set these headers server side (golang snippet) which zips up 16 files in different folders, this all works fine and well in chrome and ff, however doesnt work in safari. Javascript code is below

.... 
c.Response().Header().Set("Pragma", "public")
    c.Response().Header().Set("Expires", "0")
    c.Response().Header().Set("Cache-Control", "must-revalidate, post-check=0, pre-check=0")
    c.Response().Header().Set("Cache-Control", "public")
    c.Response().Header().Set("Content-Description", "File Transfer")
    c.Response().Header().Set("Content-type", "application/octet-stream")
    c.Response().Header().Set("Content-Transfer-Encoding", "binary")
    c.Response().Header().Set("Content-Lengthg", "177998")
    // header("Content-Length: ".filesize($filepath.$filename));
    filename := "launchaco.zip"
    // c.Response().Header().Set("Content-Type", "application/file")
    c.Response().Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=\"%s\"", filename))

    zw := zip.NewWriter(c.Response())

    header := &zip.FileHeader{
        Name:         "index.html",
        Method:       zip.Store,
        ModifiedTime: uint16(time.Now().UnixNano()),
        ModifiedDate: uint16(time.Now().UnixNano()),
    }
....

Javascript

fetch(document.location.origin + "/SECRET_ENDPOINT?s=" + encodeURIComponent(JSON.stringify(localStorage.getItem('structured-elm-todo-state'))))
    .then(function(response) {
        return response.blob();
    }).then(function(blob) {
        saveAs(blob, "download.zip");
        setTimeout(function() {
            var popup = document.getElementById("downloaded-popup");
            popup.className = "downloader-popup downloader-popup__active"
        }, 1000);
    });