>Doesn't this mean you could implement a generic tree type if you fix the underlying data structure to be an array/map?

Nope. There are only a few functions that accept type parameters, and they must be called with concrete types, and they only work with certain aggregate types. For example, "make" can only be used to create slices, maps or channels, so you could create a slice of 10 bytes with "make([]bytes, 10)" but you cannot write "make(T)" or even "make([]T, 10)" where T is a type variable, and you also can't do "make(Tree)" where Tree is, e.g, some struct type.