Já fiz assim e está funcionando bem.
const connection = mysql.createConnection({.....});
global.db = Bluebird.promisifyAll(connection);
db.queryAsync("SELECT * FROM users").then(function(rows){
console.log(rows);});
const connection = mysql.createConnection({.....});
global.db = Bluebird.promisifyAll(connection);
db.queryAsync("SELECT * FROM users").then(function(rows){
console.log(rows);});