go/ast walk

output

node = (*ast.File) &{Doc:<nil> Package:1 Name:main Decls:[0xc42006e2d0 0xc42006e3c0] Scope:scope 0xc420054220 {
	func f
	func g
}
 Imports:[] Unresolved:[int] Comments:[]}
  node = (*ast.Ident) main
    node = (<nil>) <nil>
  node = (*ast.FuncDecl) &{Doc:<nil> Recv:<nil> Name:f Type:0xc42000a180 Body:0xc42006e2a0}
    node = (*ast.Ident) f
      node = (<nil>) <nil>
    node = (*ast.FuncType) &{Func:15 Params:0xc42006e210 Results:<nil>}
      node = (*ast.FieldList) &{Opening:21 List:[] Closing:22}
        node = (<nil>) <nil>
      node = (<nil>) <nil>
    node = (*ast.BlockStmt) &{Lbrace:24 List:[0xc420054270] Rbrace:36}
      node = (*ast.ExprStmt) &{X:0xc42005e100}
        node = (*ast.CallExpr) &{Fun:g Lparen:28 Args:[0xc42006e270] Ellipsis:0 Rparen:34}
          node = (*ast.Ident) g
            node = (<nil>) <nil>
          node = (*ast.BinaryExpr) &{X:0xc42000a140 OpPos:31 Op:+ Y:0xc42000a160}
            node = (*ast.BasicLit) &{ValuePos:29 Kind:INT Value:1}
              node = (<nil>) <nil>
            node = (*ast.BasicLit) &{ValuePos:33 Kind:INT Value:1}
              node = (<nil>) <nil>
            node = (<nil>) <nil>
          node = (<nil>) <nil>
        node = (<nil>) <nil>
      node = (<nil>) <nil>
    node = (<nil>) <nil>
  node = (*ast.FuncDecl) &{Doc:<nil> Recv:<nil> Name:g Type:0xc42000a200 Body:0xc42006e390}
    node = (*ast.Ident) g
      node = (<nil>) <nil>
    node = (*ast.FuncType) &{Func:39 Params:0xc42006e330 Results:<nil>}
      node = (*ast.FieldList) &{Opening:45 List:[0xc42005e140] Closing:51}
        node = (*ast.Field) &{Doc:<nil> Names:[n] Type:int Tag:<nil> Comment:<nil>}
          node = (*ast.Ident) n
            node = (<nil>) <nil>
          node = (*ast.Ident) int
            node = (<nil>) <nil>
          node = (<nil>) <nil>
        node = (<nil>) <nil>
      node = (<nil>) <nil>
    node = (*ast.BlockStmt) &{Lbrace:53 List:[] Rbrace:54}
      node = (<nil>) <nil>
    node = (<nil>) <nil>
  node = (<nil>) <nil>

sample.go

package main

func f() {
	g(1 + 1)
}

func g(n int) {}

walk.go

package main

import (
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"io/ioutil"
	"os"
	"strings"
)

func main() {
	if len(os.Args) < 2 {
		fmt.Println("Usage: <prog> <file>.go")
		return
	}
	fset := token.NewFileSet()
	src, err := ioutil.ReadFile(os.Args[1])
	if err != nil {
		panic(err)
	}
	node, err := parser.ParseFile(fset, os.Args[1], string(src), 0)
	if err != nil {
		panic(err)
	}
	ast.Walk(&visitor{}, node)
}

type visitor struct {
	indent int
}

func (v *visitor) Visit(node ast.Node) ast.Visitor {
	indent := strings.Repeat("  ", v.indent)
	fmt.Printf("%snode = (%T) %+v\n", indent, node, node)
	if node == nil {
		v.indent--
	} else {
		v.indent++
	}
	return v
}