go - 使用包加载器，如何更新包含注释的ast并打印结果代码

Question

给定此代码，我如何在不破坏注释节点的情况下使用额外的导入规范打印它。

https://play.golang.org/p/N6_y1ehM1Qc

package main

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

    "golang.org/x/tools/go/loader"
)

func main() {

    var conf loader.Config
    conf.ParserMode = parser.ParseComments

    f, err := conf.ParseFile("main.go", `// some comment goes here 
package main

// some comment here.

// main comment here.
func main(){
}
`)
    if err != nil {
        log.Fatal(err)
    }
    conf.CreateFromFiles("main", f)
    prog, err := conf.Load()
    if err != nil {
        log.Println(err)
    }

    g := &ast.GenDecl{}
    g.Tok = token.IMPORT
    spec := &ast.ImportSpec{
        Path: &ast.BasicLit{Value: "package/path"},
    }
    g.Specs = append(g.Specs, spec)
    f.Decls = append([]ast.Decl{g}, f.Decls...)
    _ = prog
    printer.Fprint(os.Stdout, token.NewFileSet(), f)
    //printer.Fprint(os.Stdout, prog.Fset, f)
}

该程序显示

package main // some comment goes here
// some comment here.
// main comment here.
import package/path

func main() {
}

我期望得到类似的输出(不确定import语句是在单独的第二个注释行之前还是之后)

// some comment goes here
package main

// some comment here.
import package/path

// main comment here.
func main() {
}

在更复杂的程序中，输出中断。我得到了混乱的go代码，例如

// some comment goes here
package main

import // some comment here.
package/path

// main comment here.
func main() {
}

Answer 1

对于我的特定用例，添加一个import语句，解决方案是使用astutil.AddImport，如@mkopriva所建议

astutil.AddImport(prog.Fset, f, "package/path")