golang ast parsing to extract a variable's value

ast.go

package main

import (
  "fmt"
  "go/ast"
  "go/parser"
  "go/token"
)

func main() {
  // borrowed from https://github.com/lukehoban/go-outline/blob/master/main.go#L54-L107
  fset := token.NewFileSet()
  parserMode := parser.ParseComments
  var fileAst *ast.File
  var err error

  fileAst, err = parser.ParseFile(fset, "group.go", nil, parserMode)
  if err != nil {
    panic(err)
  }

  for _, d := range fileAst.Decls {
    switch decl := d.(type) {
    case *ast.FuncDecl:
      fmt.Println("Func")
    case *ast.GenDecl:
      for _, spec := range decl.Specs {
        switch spec := spec.(type) {
        case *ast.ImportSpec:
          fmt.Println("Import", spec.Path.Value)
        case *ast.TypeSpec:
          fmt.Println("Type", spec.Name.String())
        case *ast.ValueSpec:
          for _, id := range spec.Names {
            fmt.Printf("Var %s: %v", id.Name, id.Obj.Decl.(*ast.ValueSpec).Values[0].(*ast.BasicLit).Value)
          }
        default:
          fmt.Printf("Unknown token type: %s\n", decl.Tok)
        }
      }
    default:
      fmt.Printf("Unknown declaration @\n", decl.Pos())
    }
  }
}

group.go

package main

const GroupName = "andy"