来源：https://stackoverflow.com/questions/66584571/how-to-access-x-headers-header-in-nginx-openresty
ngx.req.get_headers()['User-Agent']
来源：https://stackoverflow.com/questions/66584571/how-to-access-x-headers-header-in-nginx-openresty
ngx.req.get_headers()['User-Agent']