func DoEmptyUnaryCall(tc testpb.TestServiceClient) {
	reply, err := tc.EmptyCall(context.Background(), &testpb.Empty{})
	if err != nil {
		grpclog.Fatal("/TestService/EmptyCall RPC failed: ", err)
	}
	if !proto.Equal(&testpb.Empty{}, reply) {
		grpclog.Fatalf("/TestService/EmptyCall receives %v, want %v", reply, testpb.Empty{})
	}
}
DoEmptyUnaryCall performs a unary RPC with empty request and response messages.
package interop
import (
	"fmt"
	"io"
	"io/ioutil"
	"strings"
	"time"
	"github.com/golang/protobuf/proto"
	"golang.org/x/net/context"
	"golang.org/x/oauth2"
	"golang.org/x/oauth2/google"
	"google.golang.org/grpc"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/grpclog"
	testpb "google.golang.org/grpc/interop/grpc_testing"
	"google.golang.org/grpc/metadata"
)
var (
	reqSizes      = []int{27182, 8, 1828, 45904}
	respSizes     = []int{31415, 9, 2653, 58979}
	largeReqSize  = 271828
	largeRespSize = 314159
)
func clientNewPayload(t testpb.PayloadType, size int) *testpb.Payload {
	if size < 0 {
		grpclog.Fatalf("Requested a response with invalid length %d", size)
	}
	body := make([]byte, size)
	switch t {
	case testpb.PayloadType_COMPRESSABLE:
	case testpb.PayloadType_UNCOMPRESSABLE:
		grpclog.Fatalf("PayloadType UNCOMPRESSABLE is not supported")
	default:
		grpclog.Fatalf("Unsupported payload type: %d", t)
	}
	return &testpb.Payload{
		Type: t.Enum(),
		Body: body,
	}
}