allow support golang context for nomad rpc

[tantra35]

Now nomad doesn't allow make cancel for rpc calls, and with this we have some problems #4604 example). So it will be nice if nomad will implement such functionality (i suspect that is best aproach to implement this using golang context concept, for exmaple we can get this context from http Request https://golang.org/pkg/net/http/#Request.Context), so it can minimize impact of various network problems, and perhaps allowed to localize some bugs

But this approach have some troubles:

1. IMHO is relatively hard work, due it required change many signatures of methods
2. nomad use net/rpc package which is frozen now, but exist a fork of this library(https://github.com/keegancsmith/rpc) which add golang Context(https://golang.org/pkg/context/) support, but robustness of this fork not checked and it may contain some bugs
3. yamux library requires implement some Context functionalyty, but this is not too hard

[tgross]

Hi @tantra35 I just yesterday opened #7119 to discuss this. I'm going to close this issue as a dupe but let's chat about it over there!

[github-actions]

I'm going to lock this issue because it has been closed for 120 days ⏳. This helps our maintainers find and focus on the active issues.
If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.