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: read.go
    path of file: ./repos/gocryptfs/internal/readpassword
    
    the code of the file until where you have to start completion: // Package readpassword reads a password from the terminal of from stdin.
package readpassword

import (
	"bytes"
	"fmt"
	"io"
	"os"
	"os/exec"
	"
    
func readPasswordExtpass(extpass []string) ([]byte, error) {
	var parts []string
	if len(extpass) == 1 {
		parts = strings.Split(extpass[0], " ")
	} else {
		parts = extpass
	}
	tlog.Info.Printf("Reading password from extpass program %q, arguments: %q\n", parts[0], parts[1:])
	cmd := exec.Command(parts[0], parts[1:]...)
	cmd.Stderr = os.Stderr
	pipe, err := cmd.StdoutPipe()
	if err != nil {
		return nil, fmt.Errorf("extpass pipe setup failed: %v", err)
	}
	err = cmd.Start()
	if err != nil {
		return nil, fmt.Errorf("extpass cmd start failed: %v", err)
	}
	p, err := readLineUnbuffered(pipe)
	if err != nil {
		return nil, err
	}
	pipe.Close()
	err = cmd.Wait()
	if err != nil {
		return nil, fmt.Errorf("extpass program returned an error: %v", err)
	}
	if len(p) == 0 {
		return nil, fmt.Errorf("extpass: password is empty")
	}
	return p, nil
}