go install fails when using a fully qualified semver

[corbancloud-wk]

When trying to pin down dependencies in our Github Actions CI I tried to install frugal at a specific version and it failed.

go install github.com/Workiva/frugal@v3.17.6 fails with the error:
go: github.com/Workiva/frugal@v3.17.6: github.com/Workiva/frugal@v3.17.6: invalid version: module contains a go.mod file, so module path must match major version ("github.com/Workiva/frugal/v3")

As I understand this means that our go.mod is missing the major version indicator in the module name, which does seem to be the case at time of writing

frugal/go.mod

Line 1 in 81637f5

module github.com/Workiva/frugal