// Client
b, _ := ioutil.ReadFile("ca.cert")
cp := x509.NewCertPool()
if !cp.AppendCertsFromPEM(b) {
	return nil, errors.New("credentials: failed to append certificates")
}
config := &tls.Config{
	InsecureSkipVerify: false,
	RootCAs:            cp,
}
conn, err := grpc.Dial(address, grpc.WithTransportCredentials(credentials.NewTLS(config)))
if err != nil {
	log.Fatalf("did not connect: %v", err)
}
defer conn.Close()

// Server
creds, err := credentials.NewServerTLSFromFile("service.pem", "service.key")
if err != nil {
	log.Fatalf("Failed to setup TLS: %v", err)
}
s := grpc.NewServer(grpc.Creds(creds))
// ... register gRPC services ...
if err = s.Serve(lis); err != nil {
	log.Fatalf("failed to serve: %v", err)
}