Helmet behaves strangely when rendering is asynchronous #117
Description
I was seeing some odd behavior with meta tags in the head of the static pages in my project. I created a new basic template, added a <Head><title> This is About </title></Head> to the About container, and <Head><title> This is Home </title></Head> to the Home container, and ran yarn build.
The About-title ended up in the index.html file and the Home-title was nowhere to be seen.
I looked into it a bit, and I think the async renderToString is the culprit. It works as intended if I just remove the await keyword.
It looks like Helmet doesn't work all that well if the rendering is asynchronous. I dare not create a PR making it synchronous, because I'm sure it has some other use case I'm not aware of.