function buscarIDauto(id_gps, done) {

var valor = "";

var sql = " SELECT Concat(Coalesce(marca_veh, '-'), ',', Coalesce(modelo_veh, '-'), ',', ";
sql = sql + " Coalesce( ";
sql = sql + " placa_veh, '-'), ',', Coalesce(id_auto, '-')) AS campo1 ";
sql = sql + " FROM vehiculos ";
sql = sql + " WHERE id_gps = '" + id_gps + "' ";
sql = sql + " LIMIT 1 ";

//var devolver = "";

selectGen(sql, function (err, res) {
if (err) console.error(err);
//console.log(res);

//devolver = res;

//return res;

return done(null, res);
});

//return devolver;
}

function selectGen(callback) {

var sql = " SELECT marca_veh as campo1 FROM vehiculos limit 1 ";


var con = mysql.createConnection({
host: properties.get('main.db.param.host'),
user: properties.get('main.db.param.user'),
password: properties.get('main.db.param.password'),
database: properties.get('main.db.param.database'),
connectTimeout: parseInt(properties.get('main.db.param.connectTimeout'))
});

con.connect(function (err) {

if (err) {
console.log("ERROR ON CONNECT DB MYSQL :" + err);
return callback(err);
}

con.query(sql, function (err, result, fields) {

if (err) {
console.log("ERROR ON QUERY " + sql + " DB MYSQL :" + err);
return callback(err);
}

if (result.length > 0) {
//console.log("result[0].campo1 :" + result[0].campo1);
stuff_i_want = result[0].campo1;
return callback("calbback ok :"+result[0].campo1);
} else {
stuff_i_want = '';
return callback('');
}

});

});

}

var stuff_i_want = '';
global.varBuscarIDauto = "";

selectGen(function (result) {
stuff_i_want = result;
console.log("result " + result);
global.varBuscarIDauto = result;

return "return: "+result;
//rest of your code goes in here
});

var a = selectGen();
console.log("AAAA :"+ a);