I've been playing with this branch and I noticed Body doesn't support try_concat anymore with futures 0.3 since Chunk would need to implement Extend<u8> according to the new function signature.

the trait bound `hyper::body::chunk::Chunk: std::iter::Extend<u8>` is not satisfied
required because of the requirements on the impl of `core::future::future::Future` for `futures_util::stream::try_stream::try_concat::TryConcat<&mut hyper::body::body::Body>`

Body doesn't support try_concat anymore

True, this is because Bytes (and thus Chunk) no longer implement Extend<u8>, since they are meant to be a frozen item. I have plans to add some alternatives to the http-body trait.

@seanmonstar What about BytesMut ?