Placing links inside markdown code blocks
As far as I know, the current instance of GitHub Flavored Markdown doesn't support this.
The all block is rendered with <div class="highlight highlight-html"><pre>... </pre></div>
, meaning your markdown link is not interpreted.
It would be best to place that link just before the code section (unless said section has dozens of similar links in your code).
If its a short piece of code this should do the trick:
[`this is code`](https://this_is_url/)