net/http: use cancelKey to cancel request

Follows up on CL 245357 and adds missing returns in waitCondition (CL 477196)

Fixes golang#51354

src/net/http/transport.go

@@ -2248,7 +2248,7 @@ func (pc *persistConn) readLoop() {
 			}
 		case <-rc.req.Cancel:
 			alive = false
-			pc.t.CancelRequest(rc.req)
+			pc.t.cancelRequest(rc.cancelKey, errRequestCanceled)
 		case <-rc.req.Context().Done():
 			alive = false
 			pc.t.cancelRequest(rc.cancelKey, rc.req.Context().Err())

src/net/http/transport_test.go

@@ -2440,6 +2440,7 @@ func testTransportCancelRequest(t *testing.T, mode testMode) {
 			if d > 0 {
 				t.Logf("pending requests = %d after %v (want 0)", n, d)
 			}
+			return false
 		}
 		return true
 	})
@@ -2599,6 +2600,65 @@ func testCancelRequestWithChannel(t *testing.T, mode testMode) {
 			if d > 0 {
 				t.Logf("pending requests = %d after %v (want 0)", n, d)
 			}
+			return false
+		}
+		return true
+	})
+}
+
+// Issue 51354
+func TestCancelRequestWithBodyWithChannel(t *testing.T) {
+	run(t, testCancelRequestWithBodyWithChannel, []testMode{http1Mode})
+}
+func testCancelRequestWithBodyWithChannel(t *testing.T, mode testMode) {
+	if testing.Short() {
+		t.Skip("skipping test in -short mode")
+	}
+
+	const msg = "Hello"
+	unblockc := make(chan struct{})
+	ts := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, r *Request) {
+		io.WriteString(w, msg)
+		w.(Flusher).Flush() // send headers and some body
+		<-unblockc
+	})).ts
+	defer close(unblockc)
+
+	c := ts.Client()
+	tr := c.Transport.(*Transport)
+
+	req, _ := NewRequest("POST", ts.URL, strings.NewReader("withbody"))
+	cancel := make(chan struct{})
+	req.Cancel = cancel
+
+	res, err := c.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	body := make([]byte, len(msg))
+	n, _ := io.ReadFull(res.Body, body)
+	if n != len(body) || !bytes.Equal(body, []byte(msg)) {
+		t.Errorf("Body = %q; want %q", body[:n], msg)
+	}
+	close(cancel)
+
+	tail, err := io.ReadAll(res.Body)
+	res.Body.Close()
+	if err != ExportErrRequestCanceled {
+		t.Errorf("Body.Read error = %v; want errRequestCanceled", err)
+	} else if len(tail) > 0 {
+		t.Errorf("Spurious bytes from Body.Read: %q", tail)
+	}
+
+	// Verify no outstanding requests after readLoop/writeLoop
+	// goroutines shut down.
+	waitCondition(t, 10*time.Millisecond, func(d time.Duration) bool {
+		n := tr.NumPendingRequestsForTesting()
+		if n > 0 {
+			if d > 0 {
+				t.Logf("pending requests = %d after %v (want 0)", n, d)
+			}
+			return false
 		}
 		return true
 	})