Simple Go gRPC Client

main.go

package main

import (
	"context"
	"flag"
	"fmt"
	"log"

	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"

	"api"
)

var (
	tls                = flag.Bool("tls", true, "Connection uses TLS if true, else plain TCP")
	caFile             = flag.String("ca_file", "", "The file containning the CA root cert file")
  	serverAddr         = flag.String("server_addr", "<api-gateway-host>:443", "The server address in the format of host:port")
	serverHostOverride = flag.String("server_host_override", "<api-gateway-host>", "The server name use to verify the hostname returned by TLS handshake")
)

func main() {
	flag.Parse()
	var opts []grpc.DialOption
	if *tls {
		creds, err := credentials.NewClientTLSFromFile(*caFile, *serverHostOverride)
		if err != nil {
			log.Fatalf("Failed to create TLS credentials %v", err)
		}
		opts = append(opts, grpc.WithTransportCredentials(creds))
		opts = append(opts, grpc.WithWaitForHandshake())
	} else {
		opts = append(opts, grpc.WithInsecure())
	}
	conn, err := grpc.Dial(*serverAddr, opts...)
	if err != nil {
		log.Fatalf("fail to dial: %v", err)
	}
	defer conn.Close()

	client := api.NewProdClient(conn)

	resp, err := client.Alive(context.TODO(), &api.AliveRequest{Message: "Hello"})
	if err != nil {
		log.Fatalf("err making request: %v", err)
	}

	fmt.Println(resp)
}