How can I put the page slug before the amp path?

TL;DR - I want my AMP paths to be mysite.com/:slug/amp/.

I have the following in my config.

[outputFormats]
[outputFormats.HTML]
[outputFormats.AMP]
  path = "?? - this is what i'm stuck on"

[outputs]
  home = ["HTML", "AMP"]
  page = ["HTML", "AMP"]
  post = ["HTML", "AMP"]

[permalinks]
  post = "/:slug/"

When I have a new post at say content/post/dog-toys.md its path will be mysite.com/dog-toys/ as expected.

I can’t seem to figure out how to make that same path with a /amp/ at the end work w/ hugo, except for aliases (more on that below).

I have tried:

path = ":slug/amp/" (and a few variations of leading/trailing slashes) - this doesn’t seem to ever insert the slug though.
path = "amp" - this does what I expected and makes the path mysite.com/amp/dog-toys/ for amp pages, and is the default value

So I said I can get aliases to work. What I mean is, if i have the following in a post:

slug = "dog-toys"
aliases = ["toys"]

Then I run hugo the file public/toys/amp/index.html is created by the hugo command and redirects to mysite.com/amp/dog-toys/.

I’m using hugo v0.34 if that helps, and I’m also not too picky on the end results. That is, I don’t mind mysite.com/:slug/amp/ redirecting to mysite.com/amp/:slug/, I just want to avoid broken links. I’m migrating from Ghost and all of their AMP routes were /:slug/amp/ by default.

Any suggestions on what to try next?