# 计算函数执行时间

有时候，能够知道一个计算执行消耗的时间是非常有意义的，尤其是在对比和基准测试中。最简单的一个办法就是在计算开始之前设置一个起始时候，再由计算结束时的结束时间，最后取出它们的差值，就是这个计算所消耗的时间。想要实现这样的做法，可以使用 `time` 包中的 `Now()` 和 `Sub` 函数：

```go
start := time.Now()
longCalculation()
end := time.Now()
delta := end.Sub(start)
fmt.Printf("longCalculation took this amount of time: %s\n", delta)
```

您可以查看示例 6.20 [fibonacci.go](https://github.com/yangchuansheng/the-way-to-go_ZH_CN/tree/f30ab7d8c58f85840a0afb548024b93642b518d5/eBook/examples/chapter_6/fibonacci.go) 作为实例学习。

如果您对一段代码进行了所谓的优化，请务必对它们之间的效率进行对比再做出最后的判断。在接下来的章节中，我们会学习如何进行有价值的优化操作。

## 链接

* [目录](https://github.com/yangchuansheng/the-way-to-go_ZH_CN/tree/f30ab7d8c58f85840a0afb548024b93642b518d5/eBook/directory.md)
* 上一节：[使用闭包调试](/the-way-to-go-zh-cn/di-er-bu-fen-yu-yan-de-he-xin-jie-gou-yu-ji-shu/06.0/06.10.md)
* 下一节：[通过内存缓存来提升性能](/the-way-to-go-zh-cn/di-er-bu-fen-yu-yan-de-he-xin-jie-gou-yu-ji-shu/06.0/06.12.md)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://ryanyang.gitbook.io/the-way-to-go-zh-cn/di-er-bu-fen-yu-yan-de-he-xin-jie-gou-yu-ji-shu/06.0/06.11.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.