After Go added generics in version 1.18, you can just import someone else's generic implementations of whatever of these functions you want and use them all throughout your code and never think about it. It's no longer a problem.
colors := items.Filter(_.age > 20).Map(_.color)
Instead of colors := items.Filter(func(x Item){ return x.age > 20 }).Map(func(x Item){ return x.color })
which as best as I can tell is how you'd express the same thing in Go if you had a container type with Map and Filter defined.