IMO Go is perfect for big companies and somewhat middle companies where they have some heavy traffic that needs to be addressed. I guess Golang is also easier to start with and craft something very fast as opposed to Elixir. (You can check multiple topics on elixirforum.com where people ask why their first-iteration code is slower than that in ruby/python.)
I can be wrong, but I haven't found any golang opinioned-matured web framework, because most of the community is okay with building from the ground up. This may suggest that golang would be preferable in complex/enterprise systems?
I'd choose Elixir for something that has to be done fast and be reliable and open for a lot of modifications that can be introduced without sweating.
My point of view is based on building some simple product in Elixir and doing research. Also, a previous company I worked for had Golang and Ruby stack.