Go v1.12 alpine images don't have git installed

[dmlambea]

Trying to build a module-enabled project with go build -o sample ./cmd/sample/... fails with an error:

go: github.com/stretchr/testify@v1.5.1: git init --bare in /go/pkg/mod/cache/vcs/ed2f58bca3966d01dc4666baa48276a4fab360938a8d941050d58e371e2bba77: exec: "git": executable file not found in $PATH

More recent versions of Go work flawlessly.

[wglambert]

#250 (comment)

#250 (comment)

As discussed above, adding git to the Alpine variant can currently be accomplished with a very trivial Dockerfile similar to the following:

FROM golang:1.11-alpine3.8
RUN apk add --no-cache git