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: client.go
    path of file: ./repos/Dingtalk-OpenAI/pkg/dingbot
    
    the code of the file until where you have to start completion: package dingbot

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"mime/multipart"
	"net/http"
	url2 "net/url"
	"sync"
	"time"

	"github.com/eryajf/chatgpt-dingtalk/config"
)

// OpenAPI doc: https://open.dingtalk.com/document/isvapp/upload-media-files
const (
	MediaTypeImage string = "image"
	MediaTypeVoice string = "voice"
	MediaTypeVideo string = "video"
	MediaTypeFile  string = "file"
)
const (
	MimeTypeImagePng string = "image/png"
)

type MediaUploadResult struct {
	ErrorCode    int64  `json:"errcode"`
	ErrorMessage string `json:"errmsg"`
	MediaID      s
    
func (c *DingTalkClient) getAccessTokenFromDingTalk() (*OAuthTokenResult, error) {
	// OpenAPI doc: https://open.dingtalk.com/document/orgapp/obtain-orgapp-token
	apiUrl := "https://oapi.dingtalk.com/gettoken"
	queryParams := url2.Values{}
	queryParams.Add("appkey", c.Credential.ClientID)
	queryParams.Add("appsecret", c.Credential.ClientSecret)

	// Create a new HTTP request to get the AccessToken
	req, err := http.NewRequest("GET", apiUrl+"?"+queryParams.Encode(), nil)
	if err != nil {
		return nil, err
	}

	// Send the HTTP request and parse the response body as JSON
	client := http.Client{
		Timeout: time.Second * 60,
	}
	res, err := client.Do(req)
	if err != nil {
		return nil, err
	}
	defer res.Body.Close()
	body, err := io.ReadAll(res.Body)
	if err != nil {
		return nil, err
	}
	tokenResult := &OAuthTokenResult{}
	err = json.Unmarshal(body, tokenResult)
	if err != nil {
		return nil, err
	}
	if tokenResult.ErrorCode != 0 {
		return nil, errors.New(tokenResult.ErrorMessage)
	}
	return tokenResult, nil
}