To begin with, zero values were never a great idea. It sounds better than what C does (undefined behavior), but zero values can also hide subtle bugs. The correct approach is to force values to always be initialized on declaration or make use-before-initialization an error.

Having said that, it was probably too late to fix zero values by 2009, when Go was released to the public, and this is not what the thread's OP suggested. He referred to Eiffel, which is an old language from the 1990s (at least?) that didn't initially have null-safety (or "void-safety" in Eiffel's case), but released a mechanism to do just that in 2009, shortly after Tony Hoare's talk at QCon London 2009 (no idea if they were influenced by the talk, but they did mention the "Billion Dollar Mistake" in the release notes).

Eiffel's added nullability and non-nullability markers to types (called "detachable" and "attached"), but it's also using flow-sensitive typing[1] to prevent null-dereferencing (which is the main cause for bugs).

The thread OP didn't ask to eliminate zero values or nullable types, but rather requested to have a non-nullable pointer type, and flow-sensitive typing.

If structs need to be zero-initialized, a non-nullable pointer could be forbidden in structs, or alternatively Go could make explicit initialization mandatory for structs that have non-nullable pointers. At the very least, Go could support non-nullable pointers as local stack values, and use flow-sensitive typing to prevent null dereference.

[1] https://en.wikipedia.org/wiki/Flow-sensitive_typing