Fix test

Author: Mr3zee

krpc/krpc-test/src/commonMain/kotlin/kotlinx/rpc/krpc/test/KrpcTestServiceBackend.kt

@@ -157,12 +157,19 @@ class KrpcTestServiceBackend : KrpcTestService {
         return arg1.count()
     }
 
+    @OptIn(DelicateCoroutinesApi::class)
+    @Suppress("detekt.GlobalCoroutineUsage")
     override suspend fun incomingStreamSyncCollectMultiple(
         arg1: Flow<String>,
         arg2: Flow<String>,
         arg3: Flow<String>,
     ): Int {
-        return arg1.count() + arg2.count() + arg3.count()
+        // buffer of size 1 may cause lock here without multiple coroutines
+        return listOf(
+            GlobalScope.async { arg1.count() },
+            GlobalScope.async { arg2.count() },
+            GlobalScope.async { arg3.count() },
+        ).awaitAll().sum()
     }
 
     override fun outgoingStream(): Flow<String> {