This function releases resources acquired by curl_global_init(3).
You should call curl_global_cleanup(3) once for each call you make to
curl_global_init(3), after you are done using libcurl.
This function is not thread safe. You must not call it when any other
thread in the program (i.e. a thread sharing the same memory) is running.
This doesnt just mean no other thread that is using libcurl. Because
curl_global_cleanup(3) calls functions of other libraries that are
similarly thread unsafe, it could conflict with any other thread that uses
these other libraries.
See the description in libcurl(3) of global environment requirements for
details of how to use this function.