handle auth

modzip vcs-test.golang.org/auth/or404/@v/v0.0.0-20190405155004-2234c475880e.zip vcs-test.golang.org/auth/or404@v0.0.0-20190405155004-2234c475880e .moddir

-- .access --
{
	"Username": "aladdin",
	"Password": "opensesame",
	"StatusCode": 404,
	"Message": "File? What file?"
}
-- index.html --
<!DOCTYPE html>
<html>
<meta name="go-import" content="vcs-test.golang.org/auth/or404 mod https://vcs-test.golang.org/auth/or404">
-- vcs-test.golang.org/auth/or404/@v/list --
v0.0.0-20190405155004-2234c475880e
-- vcs-test.golang.org/auth/or404/@v/v0.0.0-20190405155004-2234c475880e.info --
{"Version":"v0.0.0-20190405155004-2234c475880e","Time":"2019-04-05T15:50:04Z"}
-- vcs-test.golang.org/auth/or404/@v/v0.0.0-20190405155004-2234c475880e.mod --
module vcs-test.golang.org/auth/or404

go 1.13
-- .moddir/go.mod --
module vcs-test.golang.org/auth/or404

go 1.13
-- .moddir/or404.go --
package or404
-- vcs-test.golang.org/go/modauth404/@v/list --