[tech] Environment variables for proxies

I'm adding socks support for Agunua
<gemini://gemini.bortzmeyer.org/software/agunua/> and I was wondering
which environment variables to use to indicate the socks proxy. HTTP
clients typically use http_proxy with a pseudo-URL as value, for
instance:

export http_proxy=socks://localhost:1080/

Is there already a convention for gemini? Name the variable
gemini_proxy and use the same pseudo-URL syntax?