[Feature] Official support for koa

[lonix1]

inversify officially supports and has examples for express, restify and hapi.

What about koa? It was discussed some years ago but never pursued.

Some background:

• koa was created by the same team as express
• all express' core devs moved to koa
• koa is actively maintained and improved
• express is based on a decade-old design; koa is modern
• TJ himself recommends koa (his poor documentation comment is no longer valid)
• express is abandonware - the next version has been "in development" for half a decade... in truth it is in maintenance mode
• koa avoids callback hell by using async/await, so async work is now EASY and fun
• it is heavily used - about 300k downloads per week on npm
• ecosystem is big, there is a middleware for everything
• the only learning curve (which you can cover in 5 minutes) is that the middleware is a proper stack (unlike express), which means we can have pre- and post-hooks like in .NET and Java (think of actionfilters, global handlers, etc.!)
• koa would be very familiar to .NET devs - I know inversify was designed to be as close as possible to ASP.NET Core... this would make it possible to add even more modern goodies

Suggestion:

• there is an unofficial inversify-koa-utils, based on inversify-express-utils
• it does exactly what we are used to, but for koa
• the codebase is surprisingly small and neat
• it could be used as the basis for an official inversify-koa plugin

It looks like it's 99% of the way there, as it's a 1:1 copy of inversify-express-utils. If inversify's core devs do a code review on it, we could have good koa support very quickly. And I hereby volunteer as guinea pig # 1.

(cc. @remojansen)

[chenqing]

+1

[PodaruDragos]

if people will maintain it, I don't see a reason why not to add it. We don't even have time to do much for inversify itself. moving the burden of maintaining yet another package is not a good idea.

[ZQ-jhon]

+1