节点js功能在执行其他功能之前返回

function getUsernameAssociatedWithToken (token) {

    console.log('\n\t\tgetUsernameAssociatedWithToken');
    console.log("\t\t"+token);
    var userReturn = "";


    queryAsync(returnVal);

    function queryAsync(callback){
        connection.query("SELECT * FROM users WHERE token = '"+token+"'", function (error, results, fields) {

            if (error) {
                console.log(error);
                 callback(null);
            }

            if (results.length  > 0) {

                userReturn = results[0].user;
                callback(userReturn);


            } else {

                callback(null);
            }

        });
    };

    function returnVal(str){

    userReturn = str;
    console.log('vaaaaal');
    console.log(userReturn);

    }
    return userReturn;

}
function getUsernameAssociatedWithToken (token)