To get the most out of this book and experiment with the accompanying code, you need to have a fairly good understanding of programming in Go as well as sufficient experience working with the various tools that comprise the Go ecosystem.
In addition, the book assumes that you have a solid grasp of basic networking theory.
Finally, some of the more technical chapters in the book utilize technologies such as Docker and Kubernetes. While a priori knowledge of these technologies is not strictly required, any prior experience using these (or equivalent) systems will certainly prove beneficial in better understanding the topics discussed in those chapters.