Update/Install timeout needed.

[gregslu]

I'm using 38 vim plugins, PlugUpdate or Install often hangs on */38 (most of the times 37/38) well.. I thought it hangs, but I minimized my vim and forgot about it, and it finished! after drums 1 hour :) You really need some kind of timeout so it can jump to the next plugin, or just ignore it with the status failed. Cheers!

[junegunn]

Thanks for the report, and it's done. The default timeout for each task is set to 60 seconds, but you can change it with g:plug_timeout variable. PlugUpgrade and let me know if you see any problem.

FYI:
As mentioned in the commit message, terminating a task can leave the plugin directory in an invalid state. PlugClean will be required in that case.