Go does not perform "extremely fast idiomatically". There are a lot of cases where replacing channels with semaphores or atomics, avoiding too many go routines

Go does not perform "extremely fast idiomatically". There are a lot of cases where replacing channels with semaphores or atomics, avoiding too many go routines etc. can lead to significantly better performance. But Go does perform good enough if one uses simple idiomatic code style while making things relatively safe and maintainable. That is its huge advantage.