Persistent connection support for `raw` sockets (ngx.req.socket(true))

It seems that OpenResty doesn't support persistent connections when handling requests using ngx.req.socket(true). If one runs the code from test#15:
https://github.com/openresty/lua-nginx-module/blob/master/t/116-raw-req-socket.t#L785
Note: There is a bug with this test as err is used as both a variable and function name so one needs to be changed (e.g. sed 's/err(/errfn(/g' 116-raw-req-socket.t)

It can be seen that if a client sends more than one request (with header Connection: keep-alive) down the same TCP connection only the first one is acted on. It works fine if the client closes the connection and opens a new each time but this is inefficient. Also lua scripts can clearly handle persistent connections when using non-raw socket ngx.req.socket(). I'm wondering if there's anything missing from that test code to support persistent connections or if OpenResty (tested v1.13.6.2 & v1.15.8.1) doesn't support it? Support for it would be good.

Start with test/116-raw-req-socket.t around test 15 and reproduce the behavior after correcting the err name collision described in the issue. Compare repeated requests over one keep-alive TCP connection with the non-raw ngx.req.socket() case, then trace the raw-socket handling involved. Done means the test demonstrates that multiple requests on the same connection are handled correctly.