语法: co = coroutine.create(f)
环境: rewrite_by_lua, access_by_lua*, content_by_lua*, init_by_lua*, ngx.timer., header_filter_by_lua, body_filter_by_lua**
通过一个 Lua 函数创建一个用户的 Lua 协程，并返回一个协程对象。、
类似标准的 Lua coroutine.create API，但它是在 ngx_lua 创建的 Lua 协程环境中运行。
该 API 在 init_by_lua* 的环境中可用，是从 0.9.2 开始的。
该 API 在v0.6.0版本首次引入。
English source:
syntax: co = coroutine.create(f)
context: rewrite_by_lua, access_by_lua*, content_by_lua*, init_by_lua*, ngx.timer., header_filter_by_lua, body_filter_by_lua**
Creates a user Lua coroutines with a Lua function, and returns a coroutine object.
Similar to the standard Lua coroutine.create API, but works in the context of the Lua coroutines created by ngx_lua.
This API was first usable in the context of init_by_lua* since the 0.9.2.
This API was first introduced in the v0.6.0 release.