Demo code in GolangUK 2017.

demo3.go

package main

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

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

	cfg := &types.Config{Importer: importer.Default()}
	info := &types.Info{
		Defs: map[*ast.Ident]types.Object{},
		Uses: map[*ast.Ident]types.Object{},
	}

	if _, err = cfg.Check("main", fset, []*ast.File{f}, info); err != nil {
		log.Fatal(err)
	}

	ast.Inspect(f, func(n ast.Node) bool {
		switch n := n.(type) {
		case *ast.Ident:

			if n.Name == "Gopher" &&
				(isNamed(info.Uses[n]) || isNamed(info.Defs[n])) {
				fmt.Println(fset.Position(n.Pos()))
			}

			return false
		}
		return true
	})
}

func isNamed(o types.Object) bool {
	if o == nil {
		return false
	}
	_, ok := o.Type().(*types.Named)
	return ok
}

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
}