gohugo-theme-ananke/layouts/partials/featured.html

{{ $linkToCover := "" }}
{{ if .Params.featured_image }}
    {{ $linkToCover = .Params.featured_image }}
{{ else }}
    {{ $img := .Resources.GetMatch "**cover*.jpg" }}
    {{ with $img }}
        {{ $linkToCover = .Permalink }}
    {{ end }}
{{ end }}
{{ return $linkToCover }}