fix: remove hop-by-hop headers define in connection header beore some middleware

Co-authored-by: Julien Salleyron <julien.salleyron@gmail.com>

pkg/middlewares/connectionheader/connectionheader.go

@@ -0,0 +1,46 @@
+package connectionheader
+
+import (
+	"net/http"
+	"net/textproto"
+	"strings"
+
+	"golang.org/x/net/http/httpguts"
+)
+
+const (
+	connectionHeader = "Connection"
+	upgradeHeader    = "Upgrade"
+)
+
+// Remover removes hop-by-hop headers listed in the "Connection" header.
+// See RFC 7230, section 6.1.
+func Remover(next http.Handler) http.HandlerFunc {
+	return func(rw http.ResponseWriter, req *http.Request) {
+		var reqUpType string
+		if httpguts.HeaderValuesContainsToken(req.Header[connectionHeader], upgradeHeader) {
+			reqUpType = req.Header.Get(upgradeHeader)
+		}
+
+		removeConnectionHeaders(req.Header)
+
+		if reqUpType != "" {
+			req.Header.Set(connectionHeader, upgradeHeader)
+			req.Header.Set(upgradeHeader, reqUpType)
+		} else {
+			req.Header.Del(connectionHeader)
+		}
+
+		next.ServeHTTP(rw, req)
+	}
+}
+
+func removeConnectionHeaders(h http.Header) {
+	for _, f := range h[connectionHeader] {
+		for _, sf := range strings.Split(f, ",") {
+			if sf = textproto.TrimString(sf); sf != "" {
+				h.Del(sf)
+			}
+		}
+	}
+}