"To globally share data among all the requests handled by the same
nginx worker process, encapsulate the shared data into a Lua module,
use the Lua require builtin to import the module, and then manipulate
the shared data in Lua. This works because required Lua modules are
loaded only once and all coroutines will share the same copy of the
module (both its code and data)."
但是同一个lua module会被加载2次
