Q1: Yes but you can use `replace` directive in the `go.mod` file during the development. Follow the link below. I will also updated the article to clarify this point.

https://thewebivore.com/using-replace-in-go-mod-to-point-to-your-local-module/

Q2: I never encountered such problem but I guess you are using Go v1.11. You should upgrade your go version. You don't need `go mod init` since Go can install all imported modules automatically as long as you are running the program in "MODULE" mode. Hence make sure you have `GO111MODULE` environment variable set to `on` (preferred) or `auto`.