plugins: initial support of parallel execution

[nilslice]

This branches off of #57.

[nilslice]

@milton0825 - I think this branch is pretty close to done (aside from full integration tests with a plugin written in another language.. I may give that a shot and add it to the plugin-samples directory.

Anyway, if you could give this a look and if possible run through the tests and/or try out a plugin that would be hugely helpful.

I'll move on to your other PR in the meantime. Thanks again!

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/cc @november-yankee, @rwong, @celrenheit (if you're also interested in taking a look!)

[milton0825]

@nilslice this is awesome! I can try build a plugin and share my experience back. It may take a few days to get back to you tho

[milton0825]

I just tested it with my plugin and it works well. Great work!

[milton0825]

Just curious. what is this for?

[nilslice]

I like to do this sometimes to get an early compile-time (and often in IDEs) error that is only resolved if type plugin struct fully implements type Plugin interface.

[milton0825]

ah I see. good learning

[nilslice]

I just tested it with my plugin and it works well. Great work!

Thank you very much for testing!

I will write up some documentation for this and try to find some time to add an example plugin in another language. Feel free to add any additional thoughts, concerns, issues, etc here.

[milton0825]

cc @billonahill @astahlman @ArgentFalcon @rodaine