将NodeJS readline保存到变量中？

Question

我以某种方式无法使nodejs将readline的结果放入结果变量。我猜这与readline异步有关吗？我该怎么办才能将所有内容保存在变量中？。

var lineReader = require('readline').createInterface({
    input: require('fs').createReadStream('text.txt')
  });
var result = "Hello"; 

lineReader.on('line', function (line) {
  result += line;
});
console.log(result);
//result = "Hello"