Minimal ktor project used to reproduce issue "java.lang.NullPointerException: Current thread is not associated with any request and is not a background thread" described in https://youtrack.jetbrains.com/issue/KTOR-513
Here is the stacktrace of the issue:
java.lang.NullPointerException: Current thread is not associated with any request and is not a background thread at com.google.appengine.api.ThreadManager.getCurrentEnvironmentOrThrow(ThreadManager.java:149) at com.google.appengine.api.ThreadManager.backgroundThreadFactory(ThreadManager.java:120) at com.google.appengine.api.ThreadManager.createBackgroundThread(ThreadManager.java:140) at com.example.ApplicationKt$module$1$1.invokeSuspend(Application.kt:29) at com.example.ApplicationKt$module$1$1.invoke(Application.kt) at com.example.ApplicationKt$module$1$1.invoke(Application.kt) at io.ktor.server.routing.Route$buildPipeline$1$1.invokeSuspend(Route.kt:116) at io.ktor.server.routing.Route$buildPipeline$1$1.invoke(Route.kt) at io.ktor.server.routing.Route$buildPipeline$1$1.invoke(Route.kt) at io.ktor.util.pipeline.SuspendFunctionGun.loop(SuspendFunctionGun.kt:120) at io.ktor.util.pipeline.SuspendFunctionGun.proceed(SuspendFunctionGun.kt:78) at io.ktor.util.pipeline.SuspendFunctionGun.execute$ktor_utils(SuspendFunctionGun.kt:98) at io.ktor.util.pipeline.Pipeline.execute(Pipeline.kt:77) at io.ktor.server.routing.Routing$executeResult$$inlined$execute$1.invokeSuspend(Pipeline.kt:478) at io.ktor.server.routing.Routing$executeResult$$inlined$execute$1.invoke(Pipeline.kt) at io.ktor.server.routing.Routing$executeResult$$inlined$execute$1.invoke(Pipeline.kt) at io.ktor.util.debug.ContextUtilsKt.initContextInDebugMode(ContextUtils.kt:17) at io.ktor.server.routing.Routing.executeResult(Routing.kt:190) at io.ktor.server.routing.Routing.interceptor(Routing.kt:64) at io.ktor.server.routing.Routing$Plugin$install$1.invokeSuspend(Routing.kt:140) at io.ktor.server.routing.Routing$Plugin$install$1.invoke(Routing.kt) at io.ktor.server.routing.Routing$Plugin$install$1.invoke(Routing.kt) at io.ktor.util.pipeline.SuspendFunctionGun.loop(SuspendFunctionGun.kt:120) at io.ktor.util.pipeline.SuspendFunctionGun.proceed(SuspendFunctionGun.kt:78) at io.ktor.server.engine.BaseApplicationEngineKt$installDefaultTransformationChecker$1.invokeSuspend(BaseApplicationEngine.kt:124) at io.ktor.server.engine.BaseApplicationEngineKt$installDefaultTransformationChecker$1.invoke(BaseApplicationEngine.kt) at io.ktor.server.engine.BaseApplicationEngineKt$installDefaultTransformationChecker$1.invoke(BaseApplicationEngine.kt) at io.ktor.util.pipeline.SuspendFunctionGun.loop(SuspendFunctionGun.kt:120) at io.ktor.util.pipeline.SuspendFunctionGun.proceed(SuspendFunctionGun.kt:78) at io.ktor.util.pipeline.SuspendFunctionGun.execute$ktor_utils(SuspendFunctionGun.kt:98) at io.ktor.util.pipeline.Pipeline.execute(Pipeline.kt:77) at io.ktor.server.engine.DefaultEnginePipelineKt$defaultEnginePipeline$1$invokeSuspend$$inlined$execute$1.invokeSuspend(Pipeline.kt:478) at io.ktor.server.engine.DefaultEnginePipelineKt$defaultEnginePipeline$1$invokeSuspend$$inlined$execute$1.invoke(Pipeline.kt) at io.ktor.server.engine.DefaultEnginePipelineKt$defaultEnginePipeline$1$invokeSuspend$$inlined$execute$1.invoke(Pipeline.kt) at io.ktor.util.debug.ContextUtilsKt.initContextInDebugMode(ContextUtils.kt:17) at io.ktor.server.engine.DefaultEnginePipelineKt$defaultEnginePipeline$1.invokeSuspend(DefaultEnginePipeline.kt:123) at io.ktor.server.engine.DefaultEnginePipelineKt$defaultEnginePipeline$1.invoke(DefaultEnginePipeline.kt) at io.ktor.server.engine.DefaultEnginePipelineKt$defaultEnginePipeline$1.invoke(DefaultEnginePipeline.kt) at io.ktor.util.pipeline.SuspendFunctionGun.loop(SuspendFunctionGun.kt:120) at io.ktor.util.pipeline.SuspendFunctionGun.proceed(SuspendFunctionGun.kt:78) at io.ktor.util.pipeline.SuspendFunctionGun.execute$ktor_utils(SuspendFunctionGun.kt:98) at io.ktor.util.pipeline.Pipeline.execute(Pipeline.kt:77) at io.ktor.server.netty.NettyApplicationCallHandler$handleRequest$1$invokeSuspend$$inlined$execute$1.invokeSuspend(Pipeline.kt:478) at io.ktor.server.netty.NettyApplicationCallHandler$handleRequest$1$invokeSuspend$$inlined$execute$1.invoke(Pipeline.kt) at io.ktor.server.netty.NettyApplicationCallHandler$handleRequest$1$invokeSuspend$$inlined$execute$1.invoke(Pipeline.kt) at io.ktor.util.debug.ContextUtilsKt.initContextInDebugMode(ContextUtils.kt:17) at io.ktor.server.netty.NettyApplicationCallHandler$handleRequest$1.invokeSuspend(NettyApplicationCallHandler.kt:119) at io.ktor.server.netty.NettyApplicationCallHandler$handleRequest$1.invoke(NettyApplicationCallHandler.kt) at io.ktor.server.netty.NettyApplicationCallHandler$handleRequest$1.invoke(NettyApplicationCallHandler.kt) at kotlinx.coroutines.intrinsics.UndispatchedKt.startCoroutineUndispatched(Undispatched.kt:44) at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:112) at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:126) at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch(Builders.common.kt:56) at kotlinx.coroutines.BuildersKt.launch(Unknown Source) at io.ktor.server.netty.NettyApplicationCallHandler.handleRequest(NettyApplicationCallHandler.kt:37) at io.ktor.server.netty.NettyApplicationCallHandler.channelRead(NettyApplicationCallHandler.kt:29) at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444) at io.netty.channel.AbstractChannelHandlerContext.access$600(AbstractChannelHandlerContext.java:61) at io.netty.channel.AbstractChannelHandlerContext$7.run(AbstractChannelHandlerContext.java:425) at io.netty.util.concurrent.AbstractEventExecutor.runTask(AbstractEventExecutor.java:174) at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:167) at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:470) at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:569) at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997) at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) at io.ktor.server.netty.EventLoopGroupProxy$Companion.create$lambda$1$lambda$0(NettyApplicationEngine.kt:296) at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) at java.base/java.lang.Thread.run(Thread.java:829)