An interesting comment on the crypto section over on HN by someone who knows this area:

https://news.ycombinator.com/item?id=13567055

So this is not a good guide on cryptography; the examples given in this book are somewhat out of date and are more academic examples to illustrate a point than something you should use as a guide. There's a good link on Go crypto here from someone at coreos:

https://golangnews.com/stories/941-copy-paste-friendly-golang-crypto-crypto

The book is also quite old (2012) and written by someone more familiar with Java, so it should not be taken as a style guide or example implementation but is a good overview of the areas you'd need to cover in writing network services with Go.