[cgo] unloadLibrary is never called

We would need to call unload library with the wrapper destructor, but I am a bit helpless how this works. @qmuntal: Is there a chance you can take a look at this?

首先跟踪 cgo wrapper 的生命周期，并定位 wrapper 析构函数和 unloadLibrary 的入口点。确定析构是如何处理的，并验证释放 wrapper 时库是否会被卸载；该 issue 未提供任何指定的文件或测试。

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