I just finished Codecrafters.io Build Your Own HTTP Server course (my code, for the curious). This was my first time using Codecrafters, and I really enjoyed it. I learned a few things about the HTTP spec and about buffers and IO in Go.

The HTTP Spec

This was the biggest takeaway for me. I'm sure I've just barely scratched the surface, but before working on this server, I didn't really know what an HTTP request or response even was. I had only worked with higher level frameworks (e.g., Django), where you're handed a request object and don't really have to think about it. But just knowing the basic shape of an HTTP response (e.g., HTTP/1.1 200 OK\r\nMy-Header: foo\r\n\r\nHello world!) has given me a better understanding of how higher level web frameworks work -- and given me some intuition about the kinds of things that might go wrong.


While not strictly related to HTTP servers, I also got more hands on experience working with buffers, IO, and string/byte conversion in Go. I'm still fairly new to Go, with most of my professional experience in Python, where a lot of these lower level concerns are abstracted away. But I got much more experience with them here, and how to work with Go's ubiquitous io.Reader and io.Writer interfaces. The biggest lightbulb moment here was when working on the gzip compression feature. Noting that gzip.NewWriter(w io.Writer) *Writer can turn any writer into a gzip-compressed writer gave me a better appreciation of the power of Go's "accept interfaces, return structs" paradigm. It felt a lot like a Python decorator with less syntactical sugar, which is something I can get behind.

The HTTP server course is free this month, and I definitely recommend checking it out. I'm not associated with Codecrafters in any way. I just enjoyed the course.