Go is pretty fantastic to write agents in; it has a very good and expansive standard library and a huge mess of third-party libraries. A lot of very basic things agents tend to want to do (make HTTP requests, manage SQLite databases) are very idiomatic in Go already. It's easy to express concurrency in Go, which is nice if you're running multiple context windows and don't want to serialize your whole agent on slow model calls. It's very fast and it compiles to binaries, which, depending on how you're deploying your agent, might be a big win or might not be.