getting the original header order in HTTP/2

[reflection_probe]

ngx.req.get_headers() returns a table containing every header, but table
keys do not have a defined order. the iteration order is not stable at
runtime, even across identical requests. ngx.req.raw_header() returns a
string containing the entire pre-body request, but it's documented as
not working on HTTP/2, and also string parsing is not my favorite thing
in the world to do anyway.

is there a way to get the original header order as sent by the client in
HTTP/2?

[Junlong li]

can not do that at the moment.