I maintain remark42 and the go-pkgz libraries under one rule: whatever ships keeps working, because the cost of a break is paid by users, not by the maintainer who caused it. That means preserving released endpoints, options and APIs; supporting the oldest practical Go version; and treating a new major version as a separate line instead of an eviction notice. Previous versions receive security fixes in perpetuity, unless a fix cannot be made without a breaking change; inactive lines are labelled as such. Read the full compatibility manifesto.