Add packet timeout option and make latency more accurate

[flizaga]

Two major improvements :

• Add packet timeout option
• Improve ping rtt time accuracy on windows (to be able to go under millisecond)

Small improvement :

• Use program side time object instead of storing datetime on the packet body to get ping packet rtt. It avoids bad timing while clock is changing (for DST or on NTP sync, for example) ref : https://github.com/golang/go/issues/12914

[fkr]

@flizaga I came across the timeout a while ago and also wanted to add a default timeout - however if I understand correctly you chose 15 seconds default timeout. I would've gone for 10 (which is the default in the linux and BSD implementations of ping). (side note: windows has 4 seconds default timeout).

[SuperQ]

FYI: This project is abandoned as we are unable to maintain it due to lack of maintainers with admin rights on the repo. See #221

[flizaga]

Well, indeed, regarding the default timeout, I should have used a system default one, as it's possible to set it up to 10 for linux and BSD and 4 to windows. If I had think a bit much more I should have set the Timeout ticker every one seconds, as I don't think people would need a timeout under a second, and usually everyone will setup a integer number of seconds for the packet timeout.

Regarding the other topics : better accuracy on ping RTT both on linux/bsd and windows (and finally a ping that goes under the ms for the RTT (default Windows ping is not able to do it), what do you think ?

P.S. : it's the first time I code in Go, so I hope my code is respecting the coding standards.

[SuperQ]

See https://github.com/go-ping/ping/pull/226