Embed code snippets on the website

Thank you very much for assembling this scattered Go knowledge.

Currently only few of the mistakes have inline code snippets, readers have to open the source in a different tab and jump back and forth. It is better you could embed it directly on the website, it does not need to include imports, just the required portion. You can use https://emgithub.com/ for such things. If you think it will lengthen the page, make them folded by default.