Custom Shortcode with Timeline

[amino-8]

I'm not sure if this is a blowfish question or a question due to my misunderstanding of Hugo, but I'll ask anyway!

I'm trying to play around with the new Hugo functionality with GetRemote. 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 timeline shortcode from blowfish but it's throwing erros (I think somethign 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?