Create example of getting a reference to a resource by tag value

[Doug-AWS]

Replaces this issue created by Doug-AWS on Mar 11 in the CDK repo: aws/aws-cdk#1990.

Original description:

User wrote:

I'm trying to get a subnetId with a tag (actually the tag is applied by creation through CDK, so it's especially troublesome to not be able to find this).

In this example, you show how to apply a tag, but not how to find a resource with a Tag. Presently, I need to replace something like the following in the AWS SDK:

Filter filter = new Filter().withName("vpc-id").withValues(vpcId).withName("tag:Name").withValues("infraStack/CodeBuild VPC/PrivateSubnet1");

DescribeSubnetsRequest describeSubnetsRequest = new DescribeSubnetsRequest().withFilters(filter);

String subnetId = null;

try {
subnetId = getClient().describeSubnets(describeSubnetsRequest).getSubnets().iterator().next().getSubnetId();

Right now CDK doesn't necessarily have API or user guide documentation on how to do this--or I'm not finding it.

[Doug-AWS]

https://docs.aws.amazon.com/cdk/latest/guide/constructs.html#constructs_tagging

[russmilburn]

is there any progress on this issue? or is there a way of getting existing resources already created using tags?