If you want network buffers in Go, you can just use []byte. The Go GC is designed to make this work well, so nobody in Go is asking for a separate buffer type like you have in Java. In Java you have Buffer in the first place because there are good reasons why you might not want to use byte[].
Unboxed C types in Go can be done with cgo (it's not necessarily pleasant, but it works).
Unboxed C types in Go can be done with cgo (it's not necessarily pleasant, but it works).