Taking some random samplings of the content, this appears to be mostly rehashed OWASP Wiki content with some random, incomplete Go snippets. The password hashing content is particularly bad (unsurprising, since OWASP's password hashing content is bad). The sections are inconsistent (for instance: the crypto section recommends "AES", demonstrates [without explaining] AES-GCM, and the data protection section recommends Nacl). Very little of it addresses any kind of pitfall of programming in Go. There are places where the authors seem confused about basic Go data types (for instance, between slices and maps).

I assume this is just a starting point, and I get that bootstrapping a book from OWASP content is a legitimate way to create a starting point; I'd just say: this is definitely an early starting point.