问访问nodejs中父作用域中的变量

EN

var db_server  = "primary";
var that = this;
var startServerWith = function(db_server) {
    try {
        console.log(that.db_server);
        console.log(db_server);
                // start
    } catch (err) {
        console.log("Sever failed " , err.message);
    }
};

startServerWith("secondary");

undefined
secondary