func NewMockServer(port int, messageChan chan interface{}) {
	lis, err := net.Listen("tcp", fmt.Sprintf(":%d", 50052))
	if err != nil {
		log.Fatalf("failed to listen: %v", err)
	}
	s := MockServer{messageChan: messageChan}
	grpcServer := grpc.NewServer()
	RegisterBillingServer(grpcServer, &s)
	if err := grpcServer.Serve(lis); err != nil {
		log.Fatalf("failed to serve: %s", err)
	}
}
NewMockServer creates a new mock billing gRPC server
package billing
import (
	context "context"
	fmt "fmt"
	"log"
	"net"
	"github.com/weworksandbox/sg2019/pkg/mock"
	grpc "google.golang.org/grpc"
)