This article is the 19th entry for the Makuake Advent Calendar 2023.

The reason for this delay is that I decided to fill the only remaining slot for the 19th day at the last minute. Since it wasn't my original slot, it's technically not late.

Overview

Since last year, there has been a proposal to extend the functionality of Go's net/http ServeMux, which I had been keeping an eye on. Recently, it seems the proposal was closed.

cf. net/http: enhanced ServeMux routing #61410
cf. Proposal for enhancing ServeMux functionality in Go accepted

This extension is expected to be included in Go1.22, and since Go1.22rc2 has been released, I decided to give it a try. (It seems to have been included since Go1.22rc1, but I missed it.)

Changes to net/http in Go1.22

Looking at the details listed in tip.golang.org/doc/go1.22#net/http, the following changes have been made:

• Added ServeFileFSs, FileServerFS, and NewFileTransportFS
• HTTP servers and clients now reject requests and responses with invalid empty Content-Length headers
• Added Request.PathValue and Request.SetPathValue

From this information alone, it's not entirely clear how the routing specifications have changed, so I referred to the documentation, which provides more details.

cf. pkg.go.dev/net/http@go1.22rc2#ServeMux

I haven't followed all the details of the Proposal, but it seems that the routing pattern matching specifications proposed in the proposal have become as robust as third-party routers.

To highlight the key points, it now supports pattern matching using HTTP method names and path parameters.

Trying out the new ServeMux features in Go1.22rc2

You can download go1.22rc2 from go.dev/dl - All releases and try it out.

The use of {$} and defining methods and routes together might not be common in third-party routers (or maybe I just don't know about it...).

Regarding backward compatibility, details are provided in pkg.go.dev/net/http@go1.22rc2#hdr-Compatibility.

If you want to retain the behavior of Go1.21, you need to set the GODEBUG environment variable to httpmuuxgo121=1.

Thoughts

It feels like there's no longer a need for my custom router, goblin. For personal projects, I think I'll start transitioning to the new ServeMux.