client: always cancel in-flight request when do request

This fits the way for go1.5 to cancel request.

client/cancelreq.go

@@ -0,0 +1,20 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// borrowed from golang/net/context/ctxhttp/cancelreq.go
+
+// +build go1.5
+
+package client
+
+import "net/http"
+
+func requestCanceler(tr CancelableTransport, req *http.Request) func() {
+	ch := make(chan struct{})
+	req.Cancel = ch
+
+	return func() {
+		close(ch)
+	}
+}

client/cancelreq_go14.go

@@ -0,0 +1,17 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// borrowed from golang/net/context/ctxhttp/cancelreq_go14.go
+
+// +build !go1.5
+
+package client
+
+import "net/http"
+
+func requestCanceler(tr CancelableTransport, req *http.Request) func() {
+	return func() {
+		tr.CancelRequest(req)
+	}
+}

client/client.go

@@ -384,6 +384,8 @@ func (c *simpleHTTPClient) Do(ctx context.Context, act httpAction) (*http.Respon
 	}
 	defer hcancel()
 
+	reqcancel := requestCanceler(c.transport, req)
+
 	rtchan := make(chan roundTripResponse, 1)
 	go func() {
 		resp, err := c.transport.RoundTrip(req)
@@ -399,7 +401,7 @@ func (c *simpleHTTPClient) Do(ctx context.Context, act httpAction) (*http.Respon
 		resp, err = rtresp.resp, rtresp.err
 	case <-hctx.Done():
 		// cancel and wait for request to actually exit before continuing
-		c.transport.CancelRequest(req)
+		reqcancel()
 		rtresp := <-rtchan
 		resp = rtresp.resp
 		switch {

client/client_test.go

@@ -109,25 +109,6 @@ func newFakeTransport() *fakeTransport {
 	}
 }
 
-func (t *fakeTransport) RoundTrip(*http.Request) (*http.Response, error) {
-	select {
-	case resp := <-t.respchan:
-		return resp, nil
-	case err := <-t.errchan:
-		return nil, err
-	case <-t.startCancel:
-		select {
-		// this simulates that the request is finished before cancel effects
-		case resp := <-t.respchan:
-			return resp, nil
-		// wait on finishCancel to simulate taking some amount of
-		// time while calling CancelRequest
-		case <-t.finishCancel:
-			return nil, errors.New("cancelled")
-		}
-	}
-}
-
 func (t *fakeTransport) CancelRequest(*http.Request) {
 	t.startCancel <- struct{}{}
 }

client/fake_transport_go14_test.go

@@ -0,0 +1,41 @@
+// Copyright 2015 CoreOS, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !go1.5
+
+package client
+
+import (
+	"errors"
+	"net/http"
+)
+
+func (t *fakeTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	select {
+	case resp := <-t.respchan:
+		return resp, nil
+	case err := <-t.errchan:
+		return nil, err
+	case <-t.startCancel:
+		select {
+		// this simulates that the request is finished before cancel effects
+		case resp := <-t.respchan:
+			return resp, nil
+		// wait on finishCancel to simulate taking some amount of
+		// time while calling CancelRequest
+		case <-t.finishCancel:
+			return nil, errors.New("cancelled")
+		}
+	}
+}

client/fake_transport_test.go

@@ -0,0 +1,42 @@
+// Copyright 2015 CoreOS, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build go1.5
+
+package client
+
+import (
+	"errors"
+	"net/http"
+)
+
+func (t *fakeTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	select {
+	case resp := <-t.respchan:
+		return resp, nil
+	case err := <-t.errchan:
+		return nil, err
+	case <-t.startCancel:
+	case <-req.Cancel:
+	}
+	select {
+	// this simulates that the request is finished before cancel effects
+	case resp := <-t.respchan:
+		return resp, nil
+	// wait on finishCancel to simulate taking some amount of
+	// time while calling CancelRequest
+	case <-t.finishCancel:
+		return nil, errors.New("cancelled")
+	}
+}