Override Table Default Endpoint 

  namespace bigtable = ::google::cloud::bigtable;
  [](std::string const& project_id, std::string const& instance_id,
     std::string const& table_id) {
    auto options = google::cloud::Options{}.set<google::cloud::EndpointOption>(
        "private.googleapis.com");
    auto resource = bigtable::TableResource(project_id, instance_id, table_id);
    return bigtable::Table(
        bigtable::MakeDataConnection(
            {bigtable::InstanceResource(google::cloud::Project(project_id),
                                        instance_id)},
            std::move(options)),
        resource);
  }