fwiw, you can define your own slice or map types in Go, eg.:
type foo []string
type bar map[int]string
which is for example used in the sort package [1] of the standard lib. you are free to add methods to those types. imho Go slices and maps are more like C arrays than Objects (i'll give that the maps aren't perfect). Go just isn't OOP like C++ or Java. if you want your own fancy container types, you have to build them.
i think the designers really done 90% right, which is more than many other languages i know (TCL is in the same league). with Go i at least got to keep my sanity, contrary to python etc. especially while deploying things.
then, i'm a hopeless unix fanboy.