go.mod module for v2 versions should be with v2 postfix

[agurinov]

Hi!
If I use install from readme go install github.com/segmentio/topicctl/cmd/topicctl@latest the latest v1 major will be installed:

go: downloading github.com/segmentio/topicctl v1.23.1
...

If I use v2 (as documented in go versioning) version of install command go install github.com/segmentio/topicctl/v2/cmd/topicctl@v2.0.1
the error occcures:

go: github.com/segmentio/topicctl/v2/cmd/topicctl@v2.0.1: github.com/segmentio/topicctl@v2.0.1: invalid version: module contains a go.mod file, so module path must match major version ("github.com/segmentio/topicctl/v2")

The fix is pretty simple: in go.mod module should be renamed to module github.com/segmentio/topicctl/v2

[agurinov]

Found existing PR #253