AWS Amplify – How to call GraphQL API from API Gateway lambda

Update the Amplify function grant access to the GraphQL API

? Select which capability you want to update: Lambda function (serverless function) ? Select the Lambda function you want to update: MyFunction General information | Name: MyFunction | Runtime: nodejs ... 
? Which setting do you want to update
? Resource access permissions 
? Select the categories you want this function to have access to. (Select using <space>) > api 
? Select the operations you want to permit on <YOUR_API_NAME> (Select using <space>) > Query, Mutation, Subscription You can access the following resource attributes as environment variables from your Lambda function     API_<YOUR_API_NAME>_GRAPHQLAPIENDPOINTOUTPUT     API_<YOUR_API_NAME>_GRAPHQLAPIIDOUTPUT     
API_<YOUR_API_NAME>_GRAPHQLAPIKEYOUTPUT 
? Do you want to edit the local lambda function now? No

Update the schema.graphql to include the following directives on the tables

@aws_cognito_user_pools
@aws_iam

Update the function code to make the GraphQL call from the lambda function:

const appsyncUrl = process.env.API_<YOUR_API_NAME>_GRAPHQLAPIENDPOINTOUTPUT;

module.exports = function (req, res) {
    
    const getEmployeeById = {
      query: print(getEmployeByIdGQL),
      variables: { 
        employeeId: req.body.employeeId
      }
    };

    

    const data = JSON.stringify(req.body);
    const uri = URL.parse(appsyncUrl);
    const httpRequest = new AWS.HttpRequest(uri.href, env.REGION);
    httpRequest.headers.host = uri.host;
    httpRequest.headers['Content-Type'] = 'application/json';
    httpRequest.method = 'POST';
    httpRequest.body = JSON.stringify(getEmployeeById);
    AWS.config.credentials.get(err => {
        const signer = new AWS.Signers.V4(httpRequest, "appsync", true);
        signer.addAuthorization(AWS.config.credentials, AWS.util.date.getDate());

        const options = {
            method: httpRequest.method,
            body: httpRequest.body,
            headers: httpRequest.headers
        };

      fetch(uri.href, options)
        .then( response => {
          response.json().then(resEmployee => {
             res.json(resEmployee);
                              })
             });
       });