Shortcode from within a custom shortcode

Hello,
I’ve been reading up on how to define shortcodes with inner and outer concepts but I’m still pretty lost.
I’ve created a custom shortcode to display a list of data I’m retrieving from a JSON source. I would like to format the output using the shortcode from my theme but it’s throwing errors (I think something to do with nested shortcodes.
The code in my rsspull.html file (located in layouts/shortcodes) is:

{{ if .Get "url" }}
{{ $url := .Get "url" }}
{{ $limit := .Get "limit" }}


    {{- with .Parent -}}
    {{< timeline >}}
    {{ with resources.GetRemote $url | transform.Unmarshal }}
    {{ range first $limit .items }}
    {{< timelineItem icon="link" header="{{ .title }}" badge="{{ dateFormat "January 2, 2006" .date_modified }}" >}}
    <a href="{{ .url }}" target="_blank">{{ .title }}</a>
    {{< /timelineItem >}}
    {{ end }}
    {{ end }}
    {{< /timeline >}}
    {{- end -}}

{{ end }}

and I’m trying to call my shortcode from a md file with:

{{< rsspull url="https://link/to/json" limit="5" >}}

The error I’m getting is:

process: "/site/layouts/shortcodes/rsspull.html:7:1": parse failed unexpected "<" in command 

which points at the {{< timeline >}} code in my file.

Can anyone point me in the right direction?

You can’t call a shortcode from within a shortcode.