Demo code in GolangUK 2017.

demo2.go

package main

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

func main() {
	fset := token.NewFileSet()
	f, err := parser.ParseFile(fset, "gopher.go", nil, 0)
	if err != nil {
		log.Fatal(err)
	}

	ast.Inspect(f, func(n ast.Node) bool {
		switch n := n.(type) {
		case *ast.Ident:
			if n.Name == "Gopher" {
				fmt.Println(fset.Position(n.Pos()))
			}
			return false
		}
		return true
	})
}

gopher.go

package main

import "fmt"

type Gopher struct {
	Gopher string `json:"gopher"`
}

func main() {
	const gopher = "GOPHER"
	gogopher := GOPHER()
	gogopher.Gopher = gopher
	fmt.Println(gogopher)
}

func GOPHER() (gopher *Gopher) {
	gopher = &Gopher{Gopher: "gopher"}
	return
}