code: @Override
      public GetAppResult getApp(GetAppRequest request) {
          request = beforeClientExecution(request);
          return executeGetApp(request);
      }
docs: <p>
  Retrieves an existing Amplify App by appId.
  </p>
  
  @param getAppRequest
  Request structure for get App request.
  @return Result of the GetApp operation returned by the service.
  @throws BadRequestException
  Exception thrown when a request contains unexpected data.
  @throws NotFoundException
  Exception thrown when an entity has not been found during an operation.
  @throws UnauthorizedException
  Exception thrown when an operation fails due to a lack of access.
  @throws InternalFailureException
  Exception thrown when the service fails to perform an operation due to an internal issue.
  @sample AWSAmplify.GetApp
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/amplify-2017-07-25/GetApp" target="_top">AWS API
  Documentation</a>