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

examples/features/metadata_interceptor/client/main.go

@@ -0,0 +1,114 @@
+/*
+ *
+ * Copyright 2022 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 receive metadata in RPC headers
+// and trailers.
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"time"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+	"google.golang.org/grpc/metadata"
+
+	pb "google.golang.org/grpc/examples/features/proto/echo"
+)
+
+var addr = flag.String("addr", "localhost:50051", "the address to connect to")
+
+func callUnaryEcho(ctx context.Context, client pb.EchoClient) {
+	var header, trailer metadata.MD
+	resp, err := client.UnaryEcho(ctx, &pb.EchoRequest{Message: "hello world"}, grpc.Header(&header), grpc.Trailer(&trailer))
+	if err != nil {
+		log.Fatalf("UnaryEcho: %v", err)
+	}
+	fmt.Println("UnaryEcho: ", resp.Message)
+
+	fmt.Println("Received headers:")
+	for k, v := range header {
+		fmt.Printf("%s: %v\n", k, v)
+	}
+
+	fmt.Println("Received trailers:")
+	for k, v := range trailer {
+		fmt.Printf("%s: %v\n", k, v)
+	}
+}
+
+func callBidiStreamingEcho(ctx context.Context, client pb.EchoClient) {
+	c, err := client.BidirectionalStreamingEcho(ctx)
+	if err != nil {
+		log.Fatalf("BidiStreamingEcho: %v", err)
+	}
+
+	if err := c.Send(&pb.EchoRequest{Message: "hello world"}); err != nil {
+		log.Fatalf("Sending echo request: %v", err)
+	}
+	c.CloseSend()
+
+	for {
+		resp, err := c.Recv()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			log.Fatalf("Receiving echo response: %v", err)
+		}
+		fmt.Println("BidiStreaming Echo: ", resp.Message)
+	}
+
+	header, err := c.Header()
+	if err != nil {
+		log.Fatalf("Receiving headers: %v", err)
+	}
+	fmt.Println("Received headers:")
+	for k, v := range header {
+		fmt.Printf("%s: %v\n", k, v)
+	}
+
+	trailer := c.Trailer()
+	fmt.Println("Received tailers:")
+	for k, v := range trailer {
+		fmt.Printf("%s: %v\n", k, v)
+	}
+}
+
+func main() {
+	flag.Parse()
+
+	conn, err := grpc.NewClient(*addr, grpc.WithTransportCredentials(insecure.NewCredentials()))
+	if err != nil {
+		log.Fatalf("grpc.NewClient(%q): %v", *addr, err)
+	}
+	defer conn.Close()
+
+	ec := pb.NewEchoClient(conn)
+
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+
+	callUnaryEcho(ctx, ec)
+
+	callBidiStreamingEcho(ctx, ec)
+}