title: Terraform aws_api_gateway_integration_response keeps wanting to change attribute
body: <p>Terraform aws_api_gateway_integration_response keeps wanting to change selection_pattern attribute. Any guidance would be appreciated.</p>
  
  <pre><code>
  resource "aws_api_gateway_integration_response" "api_gateway_integration_response_e1_default" {
    rest_api_id       = "${aws_api_gateway_rest_api.api_gateway_rest_api.id}"
    resource_id       = "${aws_api_gateway_resource.e1_api_gateway_resource.id}"
    http_method       = "${aws_api_gateway_method.e1_api_gateway_method.http_method}"
    status_code       = "${aws_api_gateway_method_response.api_gateway_method_response_e1_202.status_code}"
    selection_pattern = "-"
  }
  
  resource "aws_api_gateway_integration_response" "api_gateway_integration_response_e2_default" {
    rest_api_id       = "${aws_api_gateway_rest_api.api_gateway_rest_api.id}"
    resource_id       = "${aws_api_gateway_resource.e2_api_gateway_resource.id}"
    http_method       = "${aws_api_gateway_method.e2_api_gateway_method.http_method}"
    status_code       = "${aws_api_gateway_method_response.api_gateway_method_response_e2_202.status_code}"
    selection_pattern = "-"
  }
  </code></pre>
  
  <p>My terraform apply output that keeps wanting to update.</p>
  
  <pre><code>terraform apply
  ...
  An execution plan has been generated and is shown below.
  Resource actions are indicated with the following symbols:
    ~ update in-place
  
  Terraform will perform the following actions:
  
    ~ module.gateway.aws_api_gateway_integration_response.api_gateway_integration_response_e1_default
        selection_pattern: "" =&gt; "-"
  
    ~ module.gateway.aws_api_gateway_integration_response.api_gateway_integration_response_e2_default
        selection_pattern: "" =&gt; "-"
  
  
  Plan: 0 to add, 2 to change, 0 to destroy.
  
  Do you want to perform these actions?
    Terraform will perform the actions described above.
    Only 'yes' will be accepted to approve.
  </code></pre>
  
  <p>See terraform version</p>
  
  <pre><code>$ terraform version
  Terraform v0.11.14
  + provider.aws v2.32.0
  ...
  </code></pre>