net/http: Request.ReadRequest() should not delete Request.Header["Host"]

[yamada95]

I think Request.Header["Host"] should not be deleted when parsing the request.

For example, if I use the net/http to write a proxy server, listening on 127.0.0.1:8080, and issue the following command:
curl --proxy "127.0.0.1:8080" -H "Host: domain.com" "http://130.130.10.10/ping"

The proxy should deliver the Host header to origin server 130.130.10.10, but it's already deleted by Request.ReadRequest() when reading request from client(https://golang.org/src/net/http/request.go?h=http#L714). In this case, if the origin server is configured as a nginx virtual server server_name domain.com, it will return 404 because of mismatching host name.

[bradfitz]

The Host header is put into the Request.Host field:

https://golang.org/pkg/net/http/#Request

It's been like that for ages. Changing it now, regardless of whether it's a good idea, would be a incompatible change.

In any case, you seem to have a concrete problem about writing a proxy. Let's discuss that instead on one of the forums: https://golang.org/wiki/Questions