I feel like you should spend some time with Go. If I were building a startup, I would probably choose Go for core infra for being able to move quickly as a developer and write incredibly performant code with about as much mental overhead as most dynamically typed languages.
Anecdotally, I've seen it replace Java in quite a few small and medium sized established companies.
Anecdotally, I've seen it replace Java in quite a few small and medium sized established companies.