Express.js-like middleware

[ysimonson]

This adds support for express.js-like middleware. With this patch, multiple functions can be called for any given endpoint, which allows you add functionality in a compositional manner.

You can specify global middleware that is called for all requests:

web.Middleware(gzip)
web.Middleware(basicAuth)

// This endpoint will now call the following functions in order: gzip,
// basicAuth, sayHello
web.Get("/", sayHello)

And you can specify middleware on a per-endpoint basis:

// Functionally the same as the above, although other endpoints specified
// will not have gzip and basicAuth called now.
web.Get("/", gzip, basicAuth, sayHello)

Not every function in the chain has to be called. A function can "bail" the request and circumvent the execution of further middleware by calling ctx.Finish(). e.g. if basicAuth in the above examples set some headers and called ctx.Finish() because the authentication failed, sayHello will not be called.

Unit tests have been added as well, although I'm not confident that this patch is bug-free. A second pair of eyes would help greatly since I'm not too familiar with this codebase, especially the altered logic in routeHandler.

[shuhaowu]

Can't we not already accomplish this by creating a wrapper function? Something like https://github.com/shuhaowu/levelupdb/blob/master/server.go#L93

Edit: Also, this project does not seem to have a lot of activities recently. Is it still alive?

[ysimonson]

Yep, you could do that, or just call the middleware functions from the request handler. Either seems sub-optimal compared to the composability available in express.js.

There was activity a month ago, so hopefully @hoisie is just extended afk?

[ysimonson]

@hoisie is this repo dead? should I close this PR?

[dlutwuwei]

haha, just an example to construct web framework