Proguard rules for generate signed app

[jrcacd]

Warning:co.metalab.asyncawait.RetrofitExtensionsKt: can't find referenced class retrofit2.Call
Warning:co.metalab.asyncawait.RetrofitExtensionsKt$awaitSuccessful$1: can't find referenced class retrofit2.Call
Warning:co.metalab.asyncawait.RetrofitExtensionsKt$awaitSuccessful$1: can't find referenced class retrofit2.Response
Warning:co.metalab.asyncawait.RetrofitExtensionsKt$awaitSuccessful$1: can't find referenced class retrofit2.Call
Warning:co.metalab.asyncawait.RetrofitExtensionsKt$awaitSuccessful$1: can't find referenced class retrofit2.Response
Warning:co.metalab.asyncawait.RetrofitExtensionsKt$awaitSuccessful$1: can't find referenced class retrofit2.Call
Warning:co.metalab.asyncawait.RetrofitHttpError: can't find referenced class retrofit2.Response
Warning:co.metalab.asyncawait.RxExtensionsKt: can't find referenced class rx.Observable
Warning:co.metalab.asyncawait.RxExtensionsKt$await$1: can't find referenced class rx.Observable
Warning:co.metalab.asyncawait.RxExtensionsKt$await$1: can't find referenced class rx.observables.BlockingObservable
Warning:co.metalab.asyncawait.RxExtensionsKt$await$1: can't find referenced class rx.Observable
Warning:there were 29 unresolved references to classes or interfaces.
Warning:Exception while processing task java.io.IOException: Please correct the above warnings first.
Error:Execution failed for task ':app:transformClassesAndResourcesWithProguardForRelease'.

Job failed, see logs for details

[tukak]

I'm using Retrofit and not using rx, so this did the trick for me
-dontwarn rx.Observable
-dontwarn rx.observables.BlockingObservable