Transactions.associate = (models) => {
       Transactions.belongsTo(models.Currency, {
           foreignKey: 'send_currency_type',
           as: 'SType'
       });
       Transactions.belongsTo(models.Currency, {
           foreignKey: 'receive_currency_type',
           as: 'RType'
       });
   }

exports.searchTransaction = (req, res) => {
   models.Transaction.findAll({
       attributes: ['id','secretCode','sender_fullname', 'sender_passport_series', 'sender_passport_number', 'send_currency_type', 'send_amount_in_number', 'createdAt'],
       include: [{
           model: models.Currency,
           attributes: ['id', 'name'],
           as: 'CType'
       }],
       where: {
           secretCode: req.body.secretCode
       }
   }).then(result => {
       
       const obj = { test:{
           transaction_id: result[0].id,
           secretCode: result[0].secretCode,
           sender_fullname: result[0].sender_fullname,
           sender_passport_info: ${result[0].sender_passport_series} ${result[0].sender_passport_number},
           amount: result[0].send_amount_in_number,
           currency: result[0].Currency.name,
           createdAt: result[0].createdAt
       }
       }
       const array = Object.values(obj);
       res.send({
           array,
           result
       })
   });
}

because in code example here, i see only one join.