how to use singleton in eos contract? no member named 'get_or_default' [duplicate]

Question

no member named 'get_or_default'

#include <eosiolib/singleton.hpp>
struct [[eosio::table]] glo
{
    uint64_t key;
    uint32_t stamp;
    EOSLIB_SERIALIZE(glo, (key)(stamp))
};
typedef eosio::multi_index<name("glo"), glo> glob;
ACTION debug()
    {
        require_auth(get_self());
        glob g = _bet.get_or_default();
        print(g.lastplayer:, "g.seed:", g.seed);
    }

turns out: no member named 'get_or_default'