hello world in go...ast

hello.go

package main

import (
	. "go/ast"
	"go/format"
	"go/token"
	"os"
)

func main() {
	format.Node(os.Stdout, token.NewFileSet(), &File{
		Name: &Ident{Name: "main"},
		Decls: []Decl{
			&GenDecl{
				Tok: token.IMPORT,
				Specs: []Spec{
					&ImportSpec{Path: &BasicLit{Kind: token.STRING, Value: `"fmt"`}},
				},
			},
			&FuncDecl{
				Name: &Ident{
					Name: "main",
				},
				Type: &FuncType{
					Params:  &FieldList{},
					Results: &FieldList{},
				},
				Body: &BlockStmt{
					List: []Stmt{
						&ExprStmt{
							X: &CallExpr{
								Fun: &SelectorExpr{
									X:   &Ident{Name: "fmt"},
									Sel: &Ident{Name: "Println"},
								},
								Args: []Expr{
									&BasicLit{Kind: token.STRING, Value: `"Hello, playground"`},
								},
							},
						},
					},
				},
			},
		},
	})
}