Function extract_lazy_trailers 

pub fn extract_lazy_trailers<T>(
    s: Streaming<T>,
) -> (ExtractTrailersStream<T>, LazyTrailers)

Extract LazyTrailers from [Streaming] [tonic] response.

Note that LazyTrailers has inner mutability and will only hold actual data after ExtractTrailersStream is fully consumed (dropping it is not required though).