If you load this project in VSCode by way of the workspace file in the repo, you'll see that as you load each of the go files, each module's go.mod is updated to contain more dependencies. Eventually, all three go.mod files will have the same deps.
I'd expect each module's go.mod to contain only its referenced dependencies. Interestingly, if you run go mod tidy in any of the three module dirs, the unused dependencies will be stripped out -- but then VSCode, if it's still running, will inject them again.