Make `go tool minimock` work

[ruz]

Hi,

I haven't checked, but I hope it's doable without tons of changes. This makes maintaining tool dependencies so much easier.

go get -tool github.com/gojuno/minimock/v3@latest
go tool minimock ...

Above should use exact version for everybody no matter what's installed in the GOBIN dir. More on this https://tip.golang.org/doc/modules/managing-dependencies#tools

At the moment above fails with the following error:

go tool minimock -i VersionService -o ./mocks -s _mock.go -g
package github.com/gojuno/minimock/v3 is not a main package

Sure I still use go get -tool github.com/gojuno/minimock/v3@latest, but before go generate I do go install tool to get exact version in the GOBIN.

[ruz]

Ok, that's was my mistake. The right way to add minimock as a tool is the following:

go get -tool github.com/gojuno/minimock/v3/cmd/minimock