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: util_windows.go
    path of file: ./repos/podman/vendor/github.com/mattn/go-shellwords
    
    the code of the file until where you have to start completion: // +build windows

package shellwords

import (
	"fmt"
	"os"
	"os/exec"
	"strings"
)

func shellRun(line, dir string
    
func shellRun(line, dir string) (string, error) {
	var shell string
	if shell = os.Getenv("COMSPEC"); shell == "" {
		shell = "cmd"
	}
	cmd := exec.Command(shell, "/c", line)
	if dir != "" {
		cmd.Dir = dir
	}
	b, err := cmd.Output()
	if err != nil {
		if eerr, ok := err.(*exec.ExitError); ok {
			b = eerr.Stderr
		}
		return "", fmt.Errorf("%s: %w", string(b), err)
	}
	return strings.TrimSpace(string(b)), nil
}