Ensure resty.core FFI libraries are loaded to prevent potential deadlocks.

These are loaded by default in OpenResty 1.15.8.1+, but this will ensure
this library is loaded in older versions.

openresty/lua-nginx-module#1207 (comment)
#43
#220

Author: GUI

README.md

@@ -23,6 +23,7 @@ Used in production (but the internal APIs might still be in flux).
 Requirements:
 
 - [OpenResty](http://openresty.org/#Download) 1.9.7.2 or higher
+  - **Recommended:** OpenResty 1.15.8.1 or higher is recommended for best performance and stability.
   - Or nginx patched with [ssl_cert_cb_yield](https://github.com/openresty/openresty/blob/v1.11.2.2/patches/nginx-1.11.2-ssl_cert_cb_yield.patch) and built with [ngx_lua](https://github.com/openresty/lua-nginx-module#installation) 0.10.0 or higher
 - OpenSSL 1.0.2e or higher
 - [LuaRocks](http://openresty.org/#UsingLuaRocks)

lib/resty/auto-ssl.lua

@@ -1,3 +1,12 @@
+-- Ensure resty.core FFI libraries are loaded to prevent potential deadlocks in
+-- shdict. These are loaded by default in OpenResty 1.15.8.1+, but this will
+-- ensure this library is loaded in older versions.
+--
+-- https://github.com/openresty/lua-nginx-module/issues/1207#issuecomment-350742782
+-- https://github.com/auto-ssl/lua-resty-auto-ssl/issues/43
+-- https://github.com/auto-ssl/lua-resty-auto-ssl/issues/220
+require "resty.core"
+
 local _M = {}
 
 local current_file_path = package.searchpath("resty.auto-ssl", package.path)