send priority in H2 request headers

is required by Google’s QUIC implementation

h2quic/request_writer.go

@@ -42,6 +42,7 @@ func (w *requestWriter) WriteRequest(req *http.Request, dataStreamID protocol.St
 		StreamID:      uint32(dataStreamID),
 		EndHeaders:    true,
 		BlockFragment: w.hbuf.Bytes(),
+		Priority:      http2.PriorityParam{Weight: 0xff},
 	})
 }
 

h2quic/request_writer_test.go

@@ -47,6 +47,7 @@ var _ = Describe("Request", func() {
 		rw.WriteRequest(req, 1337)
 		headerFrame, headerFields := decode(headerStream.Bytes())
 		Expect(headerFrame.StreamID).To(Equal(uint32(1337)))
+		Expect(headerFrame.HasPriority()).To(BeTrue())
 		Expect(headerFields).To(HaveKeyWithValue(":authority", "quic.clemente.io"))
 		Expect(headerFields).To(HaveKeyWithValue(":method", "GET"))
 		Expect(headerFields).To(HaveKeyWithValue(":path", "/index.html?foo=bar"))