Golang is a good choice too but in my experience its nothing compared to what you can do with Erlang Queue and Elixir. Regarding your question about proxycrawl,

Golang is a good choice too but in my experience its nothing compared to what you can do with Erlang Queue and Elixir. Regarding your question about proxycrawl, I do not know honestly, I tested the service for few days on some few millions per day and it was great too. I would say they are good for a very high volume, we are still using it, so that should be a good signal to try them.