This is an introduction to cryptography for developers. It assumes that you aren't looking for cryptographic theories, but practical ways to use cryptography in your projects. It covers the basic standard building blocks, and includes some sample code to help you get started.
Good and helpful code examples of how to actually do crypto in Go. Good discussion of when you should use crypto and which non-crypto elements you need before you even start thinking about writing crypto. However, I wish the book spent more time explaining what attacks or concerns motivate their choices. A bit more explanation for readers new to cryptography would have been very helpful, and advanced readers could have skipped over it. But at least the author links to good explanations. Really good citations.