Don't expect anything fancy, or you'll be very disappointing. No Paxos or Raft implementations :), no service discoveries, no distributed orchestrations, just basic stuff - simple networking, basic serialization (by 'basic' I mean really basic, Protobuf has got almost no attention), character encoding, HTTP (yikes), HTML (yikes x 2), REST (yikes x 3). The only thing that's slightly more interesting is WebSockets.
There are plenty of examples & the good thing about them is that they are complete (not just excerpts cut out of context), but that means the obvious drawback - they are too 'chatty' & take a lot of space: in fact the book is much shorter than it appears to.
Book starts with a tiny primer on Go (as a language) - frankly it's VERY short, but totally sufficient - code used within the book is extremely simple even for Go standards (I don't think goroutines are used at all, there's not much about idiomatic Go either).
To summarize: if you're very junior or just starting with either Go or web programming (this book really isn't about general network programming), than you can pick this one, but wait for the discount (this is how I got my copy), otherwise move along, there's nothing interesting for you here.