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: vocab.go
    path of file: ./repos/gorgonia/examples/charRNN
    
    the code of the file until where you have to start completion: package main

import "strings"

const START rune = 0x02
const END rune = 0x03

// vocab related
var sentences []string
v
    
func initVocab(ss []string, thresh int) {
	s := strings.Join(ss, "")
	dict := make(map[rune]int)
	for _, r := range s {
		dict[r]++
	}

	vocab = append(vocab, START)
	vocabIndex = make(map[rune]int)

	for ch, c := range dict {
		if c >= thresh {
			// then add letter to vocab
			vocab = append(vocab, ch)
		}
	}

	vocab = append(vocab, END)

	for i, v := range vocab {
		vocabIndex[v] = i
	}

	inputSize = len(vocab)
	outputSize = len(vocab)
	epochSize = len(ss)
}