Lspconfig: set environment variables for command?

I’d like to set some environment variables for one of the language servers I use with LSP Config.

Is there a straightforward way to do this? Or do I need to do something manually, like wrap the invocation command in /usr/bin/env?

I don’t see an option for this in settings or on_new_config, so it might not be officially supported, but it also seems like an easy feature to add that I’m sure I’m not alone in wanting. So it’s possible that I just missed it.