For both these issues the answer is Go. I found Go more fun than JavaScript. I won't write Go from scratch rather I will rewrite Python to Go when I start hitting walls.
On concurrency, I hope FastAPI will help on that. But I am horrible at writing concurrency code and that is why I don't enjoy writing JS. But from my limited experience, I enjoyed goroutines.
Package management, for mission critical stuff I have to straight up use Go binaries to be honest.
I didn't mention Go in my parent comment because it will be used as a langauge to rewrite solutions and for that to happen I need to make atleast a couple hundred dollars a month to make that investment.
