Hey man, if you're getting paid then good for you. I won't knock the hustle. But I'm still surprised.
Most of the chapters in this TOC are absolute basics, that would be covered in any Golang book (e.g. writing HTTP endpoints, fetching JSON from HTTP endpoints, using goroutines, etc). And most of the leading books on the market are around 500 pages, give or take, and cover much more.
One-hundred pages with 15 code examples is basically ~15 blog posts, packaged up in eBook form. If you're able to convert that into $5-10k or more, then that's amazing! I should self-publish a small book myself. I would not have seriously considered a project like that, because quite frankly I just don't understand the target audience. Why people would pick boutique self-published options over an O'Reilly or Manning book, etc.