update go get to go install

[AkritW]

[Stoakes]

Hello,

I had a quick try at the command, I can't get it working for Go 1.18:

$ go install -v github.com/zimmski/go-mutesting/...
go: warning: "github.com/zimmski/go-mutesting/..." matched no packages

Here is a working command on my side:

go install github.com/zimmski/go-mutesting/cmd/go-mutesting@latest

[AkritW]

You are right. I tested and fixed it.