v1.5 release with go.mod support

[pkieltyka]

chi dates back to 2016 with it's original implementation as one of the first routers to adopt the newly introduced context.Context api to the stdlib -- set out to design a router that is faster, more modular and simpler than anything else out there -- while not introducing any custom handler types or dependencies. Today, chi still has zero dependencies, and in many ways is future proofed from changes, given it's minimal nature. Between versions, chi's iterations have been very incremental, with the architecture and api being the same today as it was originally designed in 2016. For this reason it makes chi a pretty easy project to maintain, as well thanks to the many amazing community contributions over the years to who all help make chi better (total of 86 contributors to date -- thanks all!).

Chi has been an labour of love, art and engineering, with the goals to offer beautiful ergonomics, flexibility, performance and simplicity when building HTTP services with Go. I've strived to keep the router very minimal in surface area / code size, and always improving the code wherever possible -- and as of today the chi package is just 1082 lines of code (not counting middlewares, which are all optional). As well, I don't have the exact metrics, but from my analysis and email exchanges from companies and developers, chi is used by thousands of projects around the world -- thank you all as there is no better form of joy for me than to have art I had started be helpful and enjoyed by others. And of course I use chi in all of my own projects too :)

For me, the asthetics of chi's code and usage are very important. With the introduction of Go's module support (which I'm a big fan of), chi's past versioning scheme choice to v2, v3 and v4 would mean I'd require the import path of "github.com/go-chi/chi/v4", leading to the lengthy discussion at #462. Haha, to some, you may be scratching your head why I've spent > 1 year stalling to adopt "/vXX" convention in the import path -- which isn't horrible in general -- but for chi, I'm unable to accept it as I strive for perfection in it's API design, aesthetics and simplicity. It just doesn't feel good to me given chi's simple nature -- I do not foresee a "v5" or "v6", and upgrading between versions in the future will also be just incremental.

I do understand versioning is a part of the API design as well, which is why the solution for a while has been to "do nothing", as Go supports both old and new import paths with/out go.mod. However, now that Go module support has had time to iron out kinks and is adopted everywhere, it's time for chi to get with the times. Luckily, I've discovered a path forward that will make me happy, while also not breaking anyone's app who adopted a prior versioning from tags in v2/v3/v4. I've made an experimental release of v1.5.0 with go.mod silently, and tested it with new and old projects, to ensure the developer experience is preserved, and it's largely unnoticed. Fortunately, Go's toolchain will check the tags of a repo and consider the "latest" tag the one with go.mod. However, you can still request a specific older tag such as v4.1.2, and everything will "just work". But new users can just go get github.com/go-chi/chi or go get github.com/go-chi/chi@latest and they will get the latest version which contains go.mod support, which is v1.5.0+. chi will not change very much over the years, just like it hasn't changed much from 4 years ago. Therefore, we will stay on v1.x from here on, starting from v1.5.0. Any breaking changes will bump a "minor" release and backwards-compatible improvements/fixes will bump a "tiny" release.

For existing projects who want to upgrade to the latest go.mod version, run: go get -u github.com/go-chi/chi@v1.5.0, which will get you on the go.mod version line (as Go's mod cache may still remember v4.x). Brand new systems can run go get -u github.com/go-chi/chi or go get -u github.com/go-chi/chi@latest to install chi, which will install v1.5.0+ built with go.mod support.

My apologies to the developers who will disagree with the decisions above, but, hope you'll try it and see it's a very minor request which is backwards compatible and won't break your existing installations.

Cheers all, happy coding!