I think Go is a pretty good choice for the purpose. It balances high-level ease of use and learning curve with decent access to the system-y parts of coding that are so important to databases. What you learn to do in Go will translate reasonably well to a true systems language if the user wanted to take database engine design to the next level.
Languages like Python or Javascript are so far removed from the system-y side of programming that the way you would implement the concepts in those languages would not translate to the way you would actually build a "real" database which is I think the purpose of the book. I think the objective isn't to teach the abstract concepts but how those concepts are expressed in real systems.
Languages like Python or Javascript are so far removed from the system-y side of programming that the way you would implement the concepts in those languages would not translate to the way you would actually build a "real" database which is I think the purpose of the book. I think the objective isn't to teach the abstract concepts but how those concepts are expressed in real systems.