package main

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

	"golang.org/x/tools/go/ast/astutil"
)

const source = `package comments//

// X comment
var X int
`

func main() {
	fset := token.NewFileSet()
	file, _ := parser.ParseFile(fset, "", source, parser.ParseComments)

	astutil.AddNamedImport(fset, file, "tar", "archive/tar")
	astutil.AddNamedImport(fset, file, "zip", "archive/zip")

	(&printer.Config{Mode: printer.TabIndent | printer.UseSpaces, Tabwidth: 8}).Fprint(os.Stdout, fset, file)
}

package comments //

import (
	tar "archive/tar"
	zip "archive/zip"
) // X comment
var X int

package comments //

import (
	tar "archive/tar"
	zip "archive/zip"
)

// X comment
var X int