Chapter 11 states:
“Follow the installation instructions found in Chapter 8, “RESTful Networking,” to install Vapor.”
when, in fact, the book never mentions Vapor prior to Chapter 11.
Instructions for anyone who needs them:
Follow https://docs.vapor.codes/3.0/install/macos/ to install vapor onto your computer
Personally I also had to fix https://www.jianshu.com/p/9aa9e123eb07 but that may have been specific to me.