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: validator.go
    path of file: ./repos/awless/aws/config
    
    the code of the file until where you have to start completion: package awsconfig

import (
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path/filepath"
	"regexp"
	"runtime"
	"sort"
	"strings"
	"text/tabwriter"

	"github.com/aws/aws-sdk-go/aws/endpoints"
	"github.com/chzyer/readline"
)

var AWSHomeDir = func() string {
	var home string
	if runtime.GOOS == "windows" { // Windows
		home = os.Getenv("USERPROFILE")
	} else {
		home = os.Getenv("HOME")
	}
	return filepath.Join(home, ".aws")
}

func ParseRegion(i string) (interface{}, error) {
	if !IsValidRegion(i) {
		return i, fmt.Errorf("'%s' is not a valid region", i)
	
    
func StdinRegionSelector() string {
	var regionItems []readline.PrefixCompleterInterface
	for _, r := range allRegions() {
		regionItems = append(regionItems, readline.PcItem(r))
	}
	var regionCompleter = readline.NewPrefixCompleter(regionItems...)

	fmt.Println("Please enter one region: (Ctrl+C to quit, Tab for completion)")
	var region string
	rl, err := readline.NewEx(&readline.Config{
		Prompt:       "> ",
		AutoComplete: regionCompleter,
	})
	if err != nil {
		fmt.Fprintf(os.Stderr, "error while selecting region: %s", err)
		return ""
	}
	defer rl.Close()

	for !IsValidRegion(region) {
		line, err := rl.Readline()
		if err == readline.ErrInterrupt || err == io.EOF {
			os.Exit(1)
		} else if err != nil {
			fmt.Fprintf(os.Stderr, "error while selecting region: %s", err)
			return ""
		}

		region = strings.TrimSpace(line)
		if !IsValidRegion(region) {
			fmt.Fprintf(os.Stderr, "'%s' is not a valid region\n", region)
		}
	}

	return region
}