You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: pty_dragonfly.go
    path of file: ./repos/delve/vendor/github.com/creack/pty
    
    the code of the file until where you have to start completion: //go:build dragonfly
// +build dragonfly

package pty

import (
	"errors"
	"os"
	"strings"
	"syscall"
	"unsafe"
)

// same code as pty_darwin.go
func open() (pty, tty *os.File, err error) {
	p, err := os.OpenFile("/dev/ptmx", os.O_RDWR, 0)
	if err != nil {
		return nil, nil, err

    
func open() (pty, tty *os.File, err error) {
	p, err := os.OpenFile("/dev/ptmx", os.O_RDWR, 0)
	if err != nil {
		return nil, nil, err
	}
	// In case of error after this point, make sure we close the ptmx fd.
	defer func() {
		if err != nil {
			_ = p.Close() // Best effort.
		}
	}()

	sname, err := ptsname(p)
	if err != nil {
		return nil, nil, err
	}

	if err := grantpt(p); err != nil {
		return nil, nil, err
	}

	if err := unlockpt(p); err != nil {
		return nil, nil, err
	}

	t, err := os.OpenFile(sname, os.O_RDWR, 0)
	if err != nil {
		return nil, nil, err
	}
	return p, t, nil
}