Function pr47::util::serializer::co_await

pub async fn co_await<'a, D, FUT, T>(
    serializer: &'a Serializer<D>, 
    lock: SerializerLock<'a, D>, 
    fut: FUT
) -> (T, SerializerLock<'a, D>) where
    D: 'static,
    FUT: Future<Output = T>,
    T: Send + Sync,