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: iter.go
    path of file: ./repos/docker-ce/components/engine/vendor/github.com/json-iterator/go
    
    the code of the file until where you have to start completion: package jsoniter

import (
	"encoding/json"
	"fmt"
	"io"
)

// ValueType the type for JSON element
type ValueType int

const (
	// InvalidValue invalid JSON element
	InvalidValue ValueType = iota
	// St
    
func (iter *Iterator) nextToken() byte {
	// a variation of skip whitespaces, returning the next non-whitespace token
	for {
		for i := iter.head; i < iter.tail; i++ {
			c := iter.buf[i]
			switch c {
			case ' ', '\n', '\t', '\r':
				continue
			}
			iter.head = i + 1
			return c
		}
		if !iter.loadMore() {
			return 0
		}
	}
}