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: objects.go
    path of file: ./repos/tengo
    
    the code of the file until where you have to start completion: package tengo

import (
	"bytes"
	"fmt"
	"math"
	"strconv"
	"strings"
	"time"

	"github.com/d5/tengo/v2/parser"
	"github.com/d5/tengo/v2/token"
)

var (
	// TrueValue represents a true value.
	TrueValue Object = &Bool{value: true}

	// FalseValue represents a false value.
	FalseValue Object = &Bo
    
func (o *String) IndexGet(index Object) (res Object, err error) {
	intIdx, ok := index.(*Int)
	if !ok {
		err = ErrInvalidIndexType
		return
	}
	idxVal := int(intIdx.Value)
	if o.runeStr == nil {
		o.runeStr = []rune(o.Value)
	}
	if idxVal < 0 || idxVal >= len(o.runeStr) {
		res = UndefinedValue
		return
	}
	res = &Char{Value: o.runeStr[idxVal]}
	return
}