Earlier quoted context omitted.
Use slices. Really, maybe we should remove container/* completely, so we don't have to answer this stuff over and over again.
Slice still restricts you to an array data structure (a continuous block of memory). How would you implement a sorted set in Go? It should be generic and type safe and efficient, please. Compare with the C++ solution.
If you need a typesafe, generic sorted set with strict efficiency needs (or things like precise control over memory layout and such) then by all means go for C++, it's been designed for that kind of constraints.