This is a similar issue (how to get some front matter data from a draft page when building a site).
basically: you could read the directory that your authors are in and use transform.Unmarshal
on .Content
to create a map to extract parameters from.
BUT
now after taking a second look at your text, you are linking to the author page… so you still want that page to render… so i think that you are using expired
wrongly. but it seems like you can use --buildExpired
on build (see: Basic usage | Hugo)