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: prefix.go
    path of file: ./repos/octant/vendor/github.com/gobwas/glob/match
    
    the code of the file until where you have to start completion: package match

import (
	"fmt"
	"strings"
	"unicode/utf8"
)

type Prefix struct {
	Prefix string
}

func NewPrefix(p string) Prefix {
	return Prefix{p}
}

func (self Prefix) Index(s string) (int, []int) {
	idx := strings.Index(s
    
func (self Prefix) Index(s string) (int, []int) {
	idx := strings.Index(s, self.Prefix)
	if idx == -1 {
		return -1, nil
	}

	length := len(self.Prefix)
	var sub string
	if len(s) > idx+length {
		sub = s[idx+length:]
	} else {
		sub = ""
	}

	segments := acquireSegments(len(sub) + 1)
	segments = append(segments, length)
	for i, r := range sub {
		segments = append(segments, length+i+utf8.RuneLen(r))
	}

	return idx, segments
}