Using 'IOException' is an error. These classes accidentally slipped to the public API surface. We neither had intent to provide a production-quality implementation nor have an intent to support them.They are removed and to migrate, you can either use a corresponding java.io type or just a copy-paste implementation from the GitHub.If you have a use-case for multiplatform IO, please report it to the https://github.com/Kotlin/kotlinx-io/issues