easy:SetOpt_DNS_Use_Global_Cache(enable)
enable value is 1, it tells curl to use a global DNS
cache that will survive between easy handle creations and deletions. This is
not thread-safe and this will use a global variable.
WARNING: this option is considered obsolete. Stop using it. Switch over
to using the share interface instead! See #CURLOPT_SHARE and
hurl.Share().