Publishing finishes with async with no result

[st3vo7]

Without async/await, publishing to s3 results in

 Starting 'publishTechnicalDocumentationInternalS3'...
 The following tasks did not complete: publishTechnicalDocumentationInternalS3
 Did you forget to signal async completion?

When declaring it as async, and awaiting it, the compiler returns success in 13ms, but no resulting files on s3 can be found.

export const publishS3 = async function (module, version)  {
    // create a new publisher using S3 options
    // http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#constructor-property
    const publisher = awspublish.create(
        {
            signatureVersion: 'v4',
            accessKeyId: '<MyKeyId>',
            secretAccessKey:  '<MyKeySecret>',
            params: {
                Bucket:  '<MyBucket>',
            },
        },
        {
            cacheFileName: 'cache',
        },
    );

    // define custom headers
    const headers = {
        'Cache-Control': 'max-age=315360000, no-transform, public',
        'x-amz-acl': 'public-read',
    };
    let prefix =  '<MyPrefix>';
    if (prefix) {
        prefix += '/';
    }
    return gulp
        .src(`./build/site/${module.toLowerCase()}/${version}/**`)
        .pipe(
            rename(function (path) {
                path.dirname = `${module.toLowerCase()}/${prefix}${path.dirname}`;
            }),
        )
        .pipe(parallelize(publisher.publish(headers), 10))
        .pipe(publisher.sync(`${module.toLowerCase()}/${prefix}`))
        .pipe(publisher.cache())
        .pipe(awspublish.reporter());
};
export const publishTechnicalDocumentationInternalS3 = async () => await publishS3('Technical-Documentation', 'internal');

So, the outcome is:

Using gulpfile ~/Documents/Limecraft/technical-documentation/gulpfile.js
 Starting 'publishTechnicalDocumentationInternalS3'...
 Finished 'publishTechnicalDocumentationInternalS3' after 11 ms

I guess it's the issue with streams and promises, and although I tried a couple of approaches (generating a Promise on my own, using stream-to-promise library), none of them seem to be working.