看了下os.Exit的代码，当code为0时可以执行某些函数？

``` func Exit(code int) { if code == 0 { // Give race detector a chance to fail the program. // Racy programs do not have the right to finish successfully. runtime_beforeExit() } syscall.Exit(code) } func runtime_beforeExit() // implemented in runtime ``` 看了源代码，当code为0时，执行runtime_beforeExit()函数，而runtime_beforeExit()函数又没有定义什么功能，我能自定义这个函数吗