In accordance with the documented support policies of the project, the Terraform Plugin SDK will be ending support for its version 1 release on July 31, 2021.
Users of the Terraform CLI are not affected by this and do not need to do anything; only maintainers of Terraform providers are impacted.
Provider developers using version 1 of the Terraform Plugin SDK are encouraged to use our SDKv2 upgrade guide to upgrade to version 2 of the Terraform Plugin SDK. Provider developers using the version of the SDK bundled into the hashicorp/terraform repository are encouraged to first follow the guide on upgrading to version 1, and then upgrade to version 2.
After July 31, 2021, bug reports and feature requests will not be accepted for version 1 of the SDK and changes will not be backported. No further releases of the version 1 line of the SDK are expected after July 31. Providers built with version 1 will not work any differently than they do today, but any bugs will not be resolved and providers may not continue functioning in the future if Terraform requires a breaking change.
If you have any questions, please reach out to the Terraform Plugin SDK team and provider developer community using our community forums.