如何操纵HCL抽象语法树？

I'm writing a compiler using HCL (HashiCorp Configuration Language) and I'm trying to manipulate the AST so that I can add my custom logic.

hclParseTree, err := hcl.Parse(input)
check(err)
spew.Dump(hclParseTree)

I've only managed to print all the tree elements by using go-spew.

Documentation is relatively vague and there are few supporting articles on the web. I tried to follow this one, but the syntax is deprecated (written in 2015).

How could I achieve something like this?

item := hclParseTree.Get("item")