HTTP/2 push support (golang 1.8) (#1215)

* WIP

* HTTP2/Push for golang 1.8

* Push plugin completed for review

* Correct build tag

* Move push plugin position

* Add build tags to tests

* Gofmt that code

* Add header/method validations

* Load push plugin

* Fixes for wrapping writers

* Push after delivering file

* Fixes, review changes

* Remove build tags, support new syntax

* Fix spelling

* gofmt -s -w .

* Gogland time

* Add interface guards

* gofmt

* After review fixes

caddyhttp/httpserver/plugin.go

@@ -459,6 +459,7 @@ var directives = []string{
 	"proxy",
 	"fastcgi",
 	"cgi", // github.com/jung-kurt/caddy-cgi
+	"push",
 	"websocket",
 	"filemanager", // github.com/hacdias/caddy-filemanager
 	"markdown",

caddyhttp/httpserver/recorder.go

@@ -2,6 +2,7 @@ package httpserver
 
 import (
 	"bufio"
+	"errors"
 	"net"
 	"net/http"
 	"time"
@@ -95,3 +96,18 @@ func (r *ResponseRecorder) CloseNotify() <-chan bool {
 	}
 	panic(NonCloseNotifierError{Underlying: r.ResponseWriter})
 }
+
+// Push resource to client
+func (r *ResponseRecorder) Push(target string, opts *http.PushOptions) error {
+	if pusher, hasPusher := r.ResponseWriter.(http.Pusher); hasPusher {
+		return pusher.Push(target, opts)
+	}
+
+	return errors.New("push is unavailable (probably chained http.ResponseWriter does not implement http.Pusher)")
+}
+
+// Interface guards
+var _ http.Pusher = (*ResponseRecorder)(nil)
+var _ http.Flusher = (*ResponseRecorder)(nil)
+var _ http.CloseNotifier = (*ResponseRecorder)(nil)
+var _ http.Hijacker = (*ResponseRecorder)(nil)

caddyhttp/httpserver/server.go

@@ -45,6 +45,7 @@ func NewServer(addr string, group []*SiteConfig) (*Server, error) {
 		sites:       group,
 		connTimeout: GracefulTimeout,
 	}
+
 	s.Server.Handler = s // this is weird, but whatever
 
 	// Disable HTTP/2 if desired