consensus.go:12:2: use of internal package github.com/hyperledger/fabric/internal/pkg/identity not allowed
Internal packages (packages that are inside a folder that has an internal folder in their path) can only be imported from packages rooted at the parent of the internal folder.
E.g. a package pkg/foo/internal/bar can be imported by the package pkg/foo/internal/baz and also from pkg/foo/baz, but cannot be imported by the package pkg nor can it be imported by pkg/bar. This is by design. This is so big, complex packages can be broken into smaller packages without having to expose internals.
You have to treat internal packages as “private” or non-existent from the “outside”.
See related: Can I develop a go package in multiple source directories?
Read more about internal packages at Command go: Internal Directories.
Internal packages are a compiler restriction. If you want to expose them (if you want to use an internal package) in your own project, you have to remove the internal folder, and then of course you have to change the imports (import paths) too.