env GOSUMDB=off

env LOCALMODPROXY=$GOPROXY
env GOPROXY=$LOCALMODPROXY,direct

go get -x -v vcs-test.golang.org/git/hello.git
stderr '# get '$LOCALMODPROXY'/vcs-test.golang.org/git/hello.git/@v/list'
! stderr '# get https://vcs-test.golang.org'

-- go.mod --
module m

go 1.18