Variable merge into my callback - RegEx Exception

When I merge a variable into my callback, it triggers a RegEx exception. I begin with this…

ex. “callback”: “https://myapp.com/something/?this={{That}}”

Exception is this after the Workload fails…

Failed to render template “e20182fa-34fc-4e2d-9700-7535aef760ad”. Validation error: “callback” with value “{{ https://myapp.com/something/?this={{That}}” fails to match the required pattern: /^(http|https)://[-0-9a-zA-Z]*.[-0-9a-zA-Z]+.[0-9a-zA-Z]/ at path: callback; Received: {{ https://myapp.com/something/?this={{That}}

It looks like the JSON changes after a workload has run. What’s weird is that sometimes it works, but most times it fails.

Any guidance?

After some testing, I found that if include my Full URL (with querystring appended) into my CSV, the JSON accepts the Full URL merge. Like this … “callback”: “{{ FullURL }}”. If I try to append the merger field into the querystring, I get a RegEx error.