SNI-based reverse proxying with Go(lang)

Short version for readers who know all about this kind of stuff: we built a simple reverse-proxy server in Go that load-balances HTTP requests using the Hosts header and HTTPS using the SNIs from the client handshake. Backends are selected per-host from sets stored in a redis database. It works pretty well, but we won't be using it because it can't send the originating client IP to the backends when it's handling HTTPS. Code here.

We've been looking at options to load-balance our user's web applications at PythonAnywhere; this post is about something we considered but eventually abandoned; I'm posting it because the code might turn out to be useful to other people.

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