services.AddSingleton<NodePackageService>(
    sp => new NodePackageService(sp,
        new NodePackageServiceOptions
        {
            // This must be unique to avoid multiple process accessing same
            // folder conflicts
            TempFolder = "D:\\temp\\" + Guid.NewGuid(),
            // ProGet private registry url
            NPMRegistry = "https://private-proget.company.com/npm/PRIVATE",
            PrivatePackages = new string[] {
                "@company/[email protected]",
                "@company/[email protected]"
            }
        }));

    [HttpGet("template/{version}/{name}")]
    public async Task<string> ProcessTemplate(
        [FromRoute] string name,
        [FromRoute] string version,
        [FromBody] EmailModel model,
        [FromService] NodePackageService packageService
    ) {

        // get node services from the installed package version
        // if version does not exist, it will download package
        // along with all its dependencies
        var package = await 
            packageService.GetInstalledPackageASync($"@company/template@{version}");

        return await package.NodeServices.InvokeExportAsync(
            "index.js",
            "default",
            new {
                fromName: "Sender",
                fromAddress: "senderEmail",
                body: model
            });

    }