I disagree. You are merely used to different conventions. In haskell, symbols starting with an uppercase are types (or Constructors). You can think about Map as

I disagree. You are merely used to different conventions. In haskell, symbols starting with an uppercase are types (or Constructors). You can think about Map as a type constructor which takes two other types as its arguments. So Map Foo Bar is a Map with Foo as keys and Bar as values. In the go version [] is used for both indexing and type definition.