NSwag & Extension Code - How to ensure it's placed at the start of the file?

Okay, I figured it out. For me, there were two issues:

1. I had a configurationClass that was actually an interface.
2. There were comments above my base class, which is apparently a no-no.

I was running into the same issue and found Matt Grande's solution didn't work for me. So here are a list of things to check which caused my problem.

1. Any comment with the word class in it above the base class seem to cause a problem.
2. There cannot be any indentation before the start of your class declaration - This either leads to the generator adding your code at the bottom or doing export export class BaseClass. (Copying from the docs adds indentation to the file)
3. Having an interface as your configrationClass seems to work but generates the configuration interface at the bottom of the file - This is still valid Typescript.