CoreWCF server no longer responds to new requests

Hi,

we use
- CoreWCF 1.1.0
- .net 4.71
with an interface similar to
` [OperationContract]
[FaultContract(typeof(FaultDetail))]
Stream QueryDataStreamed(string sqlCommand);
`
The server writes to the stream while the client reads from it.

After some time (hours) the server no longer responds to new requests and has a lot of open threads (> 500).

Start by reproducing the streamed QueryDataStreamed operation with CoreWCF 1.1.0 on .NET 4.71, then monitor request handling and open-thread counts over several hours. Done means the cause of the server becoming unresponsive is identified and a verified change prevents new requests from hanging or thread counts from growing without bound.

Written by the indexing model from the issue text.