Example for Basic AST Traversal in Go

main.go

package main

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

func main() {
	fset := token.NewFileSet()
	node, err := parser.ParseFile(fset, "test.go", nil, parser.ParseComments)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Println("########### Manual Iteration ###########")

	fmt.Println("Imports:")
	for _, i := range node.Imports {
		fmt.Println(i.Path.Value)
	}

	fmt.Println("Comments:")
	for _, c := range node.Comments {
		fmt.Print(c.Text())
	}

	fmt.Println("Functions:")
	for _, f := range node.Decls {
		fn, ok := f.(*ast.FuncDecl)
		if !ok {
			continue
		}
		fmt.Println(fn.Name.Name)
	}

	fmt.Println("########### Inspect ###########")
	ast.Inspect(node, func(n ast.Node) bool {
		// Find Return Statements
		ret, ok := n.(*ast.ReturnStmt)
		if ok {
			fmt.Printf("return statement found on line %d:\n\t", fset.Position(ret.Pos()).Line)
			printer.Fprint(os.Stdout, fset, ret)
			return true
		}
		// Find Functions
		fn, ok := n.(*ast.FuncDecl)
		if ok {
			var exported string
			if fn.Name.IsExported() {
				exported = "exported "
			}
			fmt.Printf("%sfunction declaration found on line %d: \n\t%s\n", exported, fset.Position(fn.Pos()).Line, fn.Name.Name)
			return true
		}
		return true
	})
	fmt.Println()
}

test.go

package main

import "fmt"
import "strings"

func main() {
	hello := "Hello"
	world := "World"
	words := []string{hello, world}
	SayHello(words)
}

// SayHello says Hello
func SayHello(words []string) {
	fmt.Println(joinStrings(words))
}

// joinStrings joins strings
func joinStrings(words []string) string {
	return strings.Join(words, ", ")
}