示例项目 - api-gateway-secure-pet-store（cognito，IAM，Lambda和`API网关）提及的问题here给出了以下错误：
执行登录请求时，我收到以下凭据：
"credentials": {
"accessKey": "XXXXXXXXXXXX",
"secretKey": "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX",
"sessionToken": "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",
"expiration": 1462280810000
}
但是，当我使用以上凭据并在URL / JSON下面调用Pets请求时：
网址：https://XXXXXXX.execute-api.us-east-1.amazonaws.com/devTest/pets
正文中的JSON：
{
"action": "com.amazonaws.apigatewaydemo.action.CreatePetDemoAction",
"body": {
"petId":"4",
"petType":"RabbitSumit",
"petName":"TabbitSumit",
"petAge":"41"
}
}
通过输入上述参数，它执行以下操作
{"message":"The request signature we calculated does not match the signature you provided. Check your AWS Secret Access Key and signing method. Consult the service documentation for details.\n\nThe Canonical String for this request should have been\n'POST\n/devTest/pets\n\ncontent-length:212\ncontent-type:application/x-www-form-urlencoded\nhost:XXXXXXXXX.execute-api.us-east-1.amazonaws.com\nx-amz-date:20160503T121516Z\nx-amz-security-token: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\n\ncontent-length;content-type;host;x-amz-date;x-amz-security-token\n82d7b00fc60e9684db97202b877091a3836e091224a5a8bf4567080e104e4459'\n\nThe String-to-Sign should have been\n'AWS4-HMAC-SHA256\n20160503T121516Z\n20160503/us-east-1/execute-api/aws4_request\nd6d9d29069c6575ec4510dfab1268f2ba1697a876a660c4564fe8398674f3c97'\n"}