[Announcement] SAM CLI no longer supporting Build Images on Docker Hub

The SAM CLI `sam build` command helps our customers build and manage serverless applications that may consist of various AWS Lambda supported runtimes. When your functions require a build environment to match your execution environment, you can use the `--use-container` option to access build images created and managed by AWS.

Historically, these build images have been published to Docker Hub. Starting with SAM CLI `v1.22.0` (released on April 6, 2021), these build images have also been published to Amazon Elastic Container Registry (Amazon ECR).

## Does this affect me?

If you are using SAM CLI `v1.21.0` or earlier **and** use `sam build --use-container`, this change affects you.

## When will Docker Hub support go away?

Starting December 1, 2023, SAM CLI will no longer publish build images to Docker Hub. This includes the following images:

* https://hub.docker.com/r/amazon/aws-sam-cli-build-image-python3.6
* https://hub.docker.com/r/amazon/aws-sam-cli-build-image-python3.7
* https://hub.docker.com/r/amazon/aws-sam-cli-build-image-python3.8
* https://hub.docker.com/r/amazon/aws-sam-cli-build-image-python3.9
* https://hub.docker.com/r/amazon/aws-sam-cli-build-image-nodejs12.x
* https://hub.docker.com/r/amazon/aws-sam-cli-build-image-nodejs14.x
* https://hub.docker.com/r/amazon/aws-sam-cli-build-image-java8
* https://hub.docker.com/r/amazon/aws-sam-cli-build-image-java8.al2
* https://hub.docker.com/r/amazon/aws-sam-cli-build-image-java11
* https://hub.docker.com/r/amazon/aws-sam-cli-build-image-ruby2.7
* https://hub.docker.com/r/amazon/aws-sam-cli-build-image-provided
* https://hub.docker.com/r/amazon/aws-sam-cli-build-image-provided.al2
* https://hub.docker.com/r/amazon/aws-sam-cli-build-image-go1.x
* https://hub.docker.com/r/amazon/aws-sam-cli-build-image-dotnetcore3.1

## What must I do?

Upgrade to the latest version of the SAM CLI. For instructions, see [Installing the AWS SAM CLI](https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/install-sam-cli.html). Then, when you use `sam build --use-container`, the SAM CLI will automatically retrieve your build image from Amazon ECR.