AWS　lambdaで401エラー

前提・実現したいこと

AWS lambdaを使用してAmazonLex（Bot）を呼び出し、レスポンスをLINEへ返信

発生している問題・エラーメッセージ

AWS lambdaからAmazonLexを呼び出し時に 401エラーが発生する。

2021-05-20T10:20:00.399Z	a6937f1c-2c3f-4cfd-9fb8-8a41ed893c23	ERROR	Invoke Error 	{
    "errorType": "Error",
    "errorMessage": "Request failed with status code 401",
    "statusCode": 401,
    "statusMessage": "Unauthorized",
    "originalError": {
        "message": "Request failed with status code 401",
        "name": "Error",
        "stack": "Error: Request failed with status code 401\n    at createError (/var/task/node_modules/axios/lib/core/createError.js:16:15)\n    at settle (/var/task/node_modules/axios/lib/core/settle.js:17:12)\n    at IncomingMessage.handleStreamEnd (/var/task/node_modules/axios/lib/adapters/http.js:236:11)\n    at IncomingMessage.emit (events.js:326:22)\n    at IncomingMessage.EventEmitter.emit (domain.js:483:12)\n    at endReadableNT (_stream_readable.js:1241:12)\n    at processTicksAndRejections (internal/process/task_queues.js:84:21)",
        "config": {
            "url": "https://api.line.me/v2/bot/message/reply",
            "method": "post",
            "data": "{\"messages\":[null],\"replyToken\":\"16264188ddd94dbd8b6af8db475f50d8\",\"notificationDisabled\":false}",
            "headers": {
                "Accept": "application/json, text/plain, */*",
                "Content-Type": "application/json",
                "Authorization": "Bearer チャネルアクセストークン",
                "User-Agent": "@line/bot-sdk/6.8.4",
                "Content-Length": 96
            },
            "transformRequest": [
                null
            ],
            "transformResponse": [
                null
            ],
            "timeout": 0,
            "xsrfCookieName": "XSRF-TOKEN",
            "xsrfHeaderName": "X-XSRF-TOKEN",
            "maxContentLength": -1
        }
    },
    "stack": [
        "Error: Request failed with status code 401",
        "    at HTTPClient.wrapError (/var/task/node_modules/@line/bot-sdk/dist/http.js:83:20)",
        "    at /var/task/node_modules/@line/bot-sdk/dist/http.js:19:88",
        "    at processTicksAndRejections (internal/process/task_queues.js:97:5)",
        "    at async HTTPClient.post (/var/task/node_modules/@line/bot-sdk/dist/http.js:33:21)",
        "    at async Runtime.exports.handler (/var/task/index.js:80:13)"
    ]
}

該当のソースコード

node.js
1const Line = require('@line/bot-sdk');
2const Aws = require('aws-sdk');
3const channelAccessToken = process.env.CHANNEL_ACCESS_TOKEN;
4const channelSecret = process.env.CHANNEL_SECRET;
5
6const client = new Line.Client({channelAccessToken: channelAccessToken});
7const s3 = new Aws.S3();
8
9const lex = new Aws.LexRuntime({region: 'ap-northeast-1'});
10
11const getContent = (messageId) => {
12    return new Promise((resolve, reject) => {
13        client.getMessageContent(messageId).then((stream) => {
14            let content = [];
15            stream.on('data', (chunk) => {
16                console.log('data');
17                console.log(chunk);
18                content.push(new Buffer(chunk));
19            }).on('error', (err) => {
20                reject(err);
21            }).on('end', function(){
22                console.log('end');
23                console.log(content);
24                resolve(Buffer.concat(content));
25            });
26        });
27    });
28};
29
30
31exports.handler = async(event,text,callback) => {
32    console.log(JSON.stringify(event));
33
34    //Validate signature
35    if (!Line.validateSignature(event.body, channelSecret, event.headers['x-line-signature'])) return { statusCode: 400 };
36
37    const messages = JSON.parse(event.body);
38
39    //Validate webhook from LINE Developers
40    if (messages.events.length === 0) {
41        return { statusCode: 200, body: 'OK'};
42    }
43
44    for (let i = 0; i<messages.events.length; i++) {
45        if (messages.events[i].type === 'message') {
46            let text;
47            if (messages.events[i].message.type === 'text') {
48                const params = {
49                        botAlias: 'PRD',
50                        botName: 'TESTBot',
51                        inputText:messages.events[i].message.text,
52                        userId:messages.events[i].source.userId,
53                        //sessionAttributes:{},
54                };
55            console.log(params);
56            
57           lex.postText(params,function(err,data)  {　　　←LEX呼び出しでエラー
58                    console.log("????");
59・・・以降省略
60