add a default value to TLDEXTRACT_CACHE_TIMEOUT

[guoyuqi]

if no default value defined with TLDEXTRACT_CACHE_TIMEOUT, tldextract maybe hang indefinitely since the requests never go through.

[floer32]

@guoyuqi This is a "hmmmmm" one because ... I agree for my personal preferences that I like when things don't timeout (would rather just get an error, and have my calling code be able to do retries). but kind of also thinking that requests, by design, does not specify a default timeout. so what's more astonishing to the general user, having it hang, or having it deviate from the default requests would use? Not sure!

the compromise solution is seemingly: have a default timeout but have it be very long. like 5 minutes.

what do you think @guoyuqi ?

since there is already a configuration variable for it though, there is a workaround, so i'm marking it as lower-priority than the other tickets

[john-kurkowski]

I'd defer to requests. Expect this library to default the same as the popular, familiar Python library.

[floer32]

yeah - Principle of Least Astonishment - do what someone would expect for a library that wraps requests

[floer32]

Would be good to add a note to the README though since it does not point out this environment variable being available. @guoyuqi would you want to open a PR with a readme update adding to the 'caching' section?

[floer32]

created #159 about updating README, closing this one

[floer32]

thanks again @guoyuqi !