Spring Boot app fails on Azure function App

Question

I am trying to deploy vanilla I am following below doc :

https://learn.microsoft.com/en-us/azure/developer/java/spring-framework/getting-started-with-spring-cloud-function-in-azure

on local with maven run work perfectly fine

mvn azure-functions:run -DenableDebug   

on function app deployment there is no error. but when I run the api I get below error.

I have main class defined in pom.xml, same get generated into fat jar meta-inf and I also have tried adding environment variable MAIN_CLASS

Result: Failure

Exception: IllegalArgumentException: Failed to locate main class

Stack: java.lang.IllegalStateException: Failed to initialize
at org.springframework.cloud.function.adapter.azure.AzureFunctionInstanceInjector.getInstance(AzureFunctionInstanceInjector.java:84)
at com.microsoft.azure.functions.worker.binding.ExecutionContextDataSource.getFunctionInstance(ExecutionContextDataSource.java:103)
at com.microsoft.azure.functions.worker.broker.JavaMethodInvokeInfo.invoke(JavaMethodInvokeInfo.java:20)
at com.microsoft.azure.functions.worker.broker.EnhancedJavaMethodExecutorImpl.execute(EnhancedJavaMethodExecutorImpl.java:22)
at com.microsoft.azure.functions.worker.chain.FunctionExecutionMiddleware.invoke(FunctionExecutionMiddleware.java:19)
at com.microsoft.azure.functions.worker.chain.InvocationChain.doNext(InvocationChain.java:21)
at com.microsoft.azure.functions.worker.broker.JavaFunctionBroker.invokeMethod(JavaFunctionBroker.java:125)
at com.microsoft.azure.functions.worker.handler.InvocationRequestHandler.execute(InvocationRequestHandler.java:34)
at com.microsoft.azure.functions.worker.handler.InvocationRequestHandler.execute(InvocationRequestHandler.java:10)
at com.microsoft.azure.functions.worker.handler.MessageHandler.handle(MessageHandler.java:44)
at com.microsoft.azure.functions.worker.JavaWorkerClient$StreamingMessagePeer.lambda$onNext$0(JavaWorkerClient.java:94)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
at java.base/java.lang.Thread.run(Thread.java:840)
Caused by: java.lang.IllegalStateException: Failed to discover main class. An attempt was made to discover main class as 'MAIN_CLASS' environment variable, system property as well as entry in META-INF/MANIFEST.MF (in that order).
scala
at org.springframework.cloud.function.utils.FunctionClassUtils.getStartClass(FunctionClassUtils.java:86)
at org.springframework.cloud.function.utils.FunctionClassUtils.getStartClass(FunctionClassUtils.java:63)
at org.springframework.cloud.function.adapter.azure.AzureFunctionInstanceInjector.initialize(AzureFunctionInstanceInjector.java:97)
at org.springframework.cloud.function.adapter.azure.AzureFunctionInstanceInjector.getInstance(AzureFunctionInstanceInjector.java:70)
... 15 more
Caused by: java.lang.IllegalArgumentException: Failed to locate main class
scala
at org.springframework.util.Assert.notNull(Assert.java:181)
at org.springframework.cloud.function.utils.FunctionClassUtils.getStartClass(FunctionClassUtils.java:82)
... 18 more