public static CountDownLatch awaitNextServerAndClientCallCloses(final int count) {
        final CountDownLatch newCounter = new CountDownLatch(2 * count);
        serverCounter = newCounter;
        clientCounter = newCounter;
        return newCounter;
    }
Returns a {@link CountDownLatch} that will be used in the next server and client calls and can be used to await
the respective closes. This method must be called before the call is started.

@param count The number of call closes to await.
@return The counter used to await the client call close.
@see #awaitNextClientCallCloses(int)
@see #awaitNextServerCallCloses(int)
tests/src/test/java/net/devh/boot/grpc/test/config/AwaitableServerClientCallConfiguration.java