0.25.0

• Major rework on exception-handling and cancellation in coroutines (see #333, #452 and #451):
  • New "Exception Handling" section in the guide explains exceptions in coroutines.
  • Semantics of Job.cancel resulting Boolean value changed — true means exception was handled by the job, caller shall handle otherwise.
  • Exceptions are properly propagated from children to parents.
  • Installed CoroutineExceptionHandler for a family of coroutines receives one aggregated exception in case of failure.
  • Change handleCoroutineException contract, so custom exception handlers can't break coroutines machinery.
  • Unwrap JobCancellationException properly to provide exception transparency over whole call chain.
• Introduced support for thread-local elements in coroutines context (see #119):
  • ThreadContextElement API for custom thread-context sensitive context elements.
  • ThreadLocal.asContextElement() extension function to convert an arbitrary thread-local into coroutine context element.
  • New "Thread-local data" subsection in the guide with examples.
  • SLF4J Mapped Diagnostic Context (MDC) integration is provided via MDCContext element defined in kotlinx-coroutines-slf4j integration module.
• Introduced IO dispatcher to offload blocking I/O-intensive tasks (see #79).
• Introduced ExecutorCoroutineDispatcher instead of CloseableCoroutineDispatcher (see #385).
• Built with Kotlin 1.2.61 and Kotlin/Native 0.8.2.
• JAR files for kotlinx-coroutines are now JEP 238 multi-release JAR files.
  • On JDK9+ VarHandle is used for atomic operations instead of Atomic*FieldUpdater for better performance.
  • See AtomicFu project for details.
• Reversed addition of BlockingChecker extension point to control where runBlocking can be used (see #227).
  • runBlocking can be used anywhere without limitations (again), but it would still cause problems if improperly used on UI thread.
• Corrected return-type of EventLoop pseudo-constructor (see #477, PR by @Groostav).
• Fixed as*Future() integration functions to catch all Throwable exceptions (see #469).
• Fixed runBlocking cancellation (see #501).
• Fixed races and timing bugs in withTimeoutOrNull (see #498).
• Execute EventLoop.invokeOnTimeout in DefaultDispatcher to allow busy-wait loops inside runBlocking (see #479).
• Removed kotlinx-coroutines-io module from the project, it has moved to kotlinx-io.
• Provide experimental API to create limited view of experimental dispatcher (see #475).
• Various minor fixes by @LouisCAD, @Dmitry-Borodin.