I know of someone who published a book on Golang in 2010. The rating of that book is sitting in the 3s out of 5 stars last I checked 6 years ago. Is he an expert at Go? Not in my most humblest opinion, is the content of the book good? Also a no in my honest, must charitable view. How far did he get with showing people how to program with Go? About as far as you'd get in 2 hours on the golang docs even considering a very poorly skilled college student doing the exercises. There's maybe 170 pages in the book. I'm almost certain the book has not reached even 200 sales at the highest.

Is he really considered an expert to you, solely because of the publishing of a book? Here it is by the way: https://www.amazon.com/Go-Programming-John-P-Baugh/dp/145363...

I know that's not necessarily your view, but this is the standard we are working with