defer 关键字（参看 6.4）对于在函数结束时关闭打开的文件非常有用，例如下面的代码片段：
defer
func data(name string) string { f, _ := os.OpenFile(name, os.O_RDONLY, 0) defer f.Close() // idiomatic Go code! contents, _ := ioutil.ReadAll(f) return string(contents) }
在函数 return 后执行了 f.Close()
f.Close()
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