Where to store global settings in filter

[Jerry OELoo]

Hi All:
I have some settings in a json file (not in nginx.conf file),
Currently, in my module filter function, I will open file, read file,
close file every time filter function is called.
I think this is not so good, so I think it's better call a function
just one time, and save the setting in a global variable, but I do not
where is a proper position in Nginx module, Thanks!

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