Except the Go's implementation is not as capable as Java's one.

Phil Walder delivered a design within Go's team goals.

Java team has told nothing to Go's team, they have acknowldeged their bias anti-generics.

". They are likely the two most difficult parts of any design for parametric polymorphism. In retrospect, we were biased too much by experience with C++ without concepts and Java generics. We would have been well-served to spend more time with CLU and C++ concepts earlier."

https://go.googlesource.com/proposal/+/master/design/go2draf...