snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

examples/features/cancellation/client/main.go

@@ -0,0 +1,96 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * 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.
+ *
+ */
+
+// Binary client demonstrates how to cancel in-flight RPCs by canceling the
+// context passed to the RPC.
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"log"
+	"time"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials/insecure"
+	pb "google.golang.org/grpc/examples/features/proto/echo"
+	"google.golang.org/grpc/status"
+)
+
+var addr = flag.String("addr", "localhost:50051", "the address to connect to")
+
+func sendMessage(stream pb.Echo_BidirectionalStreamingEchoClient, msg string) error {
+	fmt.Printf("sending message %q\n", msg)
+	return stream.Send(&pb.EchoRequest{Message: msg})
+}
+
+func recvMessage(stream pb.Echo_BidirectionalStreamingEchoClient, wantErrCode codes.Code) {
+	res, err := stream.Recv()
+	if status.Code(err) != wantErrCode {
+		log.Fatalf("stream.Recv() = %v, %v; want _, status.Code(err)=%v", res, err, wantErrCode)
+	}
+	if err != nil {
+		fmt.Printf("stream.Recv() returned expected error %v\n", err)
+		return
+	}
+	fmt.Printf("received message %q\n", res.GetMessage())
+}
+
+func main() {
+	flag.Parse()
+
+	// Set up a connection to the server.
+	conn, err := grpc.NewClient(*addr, grpc.WithTransportCredentials(insecure.NewCredentials()))
+	if err != nil {
+		log.Fatalf("did not connect: %v", err)
+	}
+	defer conn.Close()
+
+	c := pb.NewEchoClient(conn)
+
+	// Initiate the stream with a context that supports cancellation.
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	stream, err := c.BidirectionalStreamingEcho(ctx)
+	if err != nil {
+		log.Fatalf("error creating stream: %v", err)
+	}
+
+	// Send some test messages.
+	if err := sendMessage(stream, "hello"); err != nil {
+		log.Fatalf("error sending on stream: %v", err)
+	}
+	if err := sendMessage(stream, "world"); err != nil {
+		log.Fatalf("error sending on stream: %v", err)
+	}
+
+	// Ensure the RPC is working.
+	recvMessage(stream, codes.OK)
+	recvMessage(stream, codes.OK)
+
+	fmt.Println("cancelling context")
+	cancel()
+
+	// This Send may or may not return an error, depending on whether the
+	// monitored context detects cancellation before the call is made.
+	sendMessage(stream, "closed")
+
+	// This Recv should never succeed.
+	recvMessage(stream, codes.Canceled)
+}