> It performs better than Go
Do you have some sources or experiences to share on this topic? I'm very curious. My experience is the complete opposite.
At my previous job there was a Java web application and running in Kubernetes (1 vCPU and 1Gi of memory) was able to deal with at most 80 requests per second, using up almost the full 1 vCPU and ~600-700MiB of memory. That was a bit disappointing, since we were supposed to support at most ~1000rps on this API, 13+ pods is a lot, and we felt "software could do better".
A reactive guru from another team told us we should use a reactive stack, so he came in and rebuilt the app using the reactive stack. Now it was doing about 120rps on one pod (about the same memory usage), which was a good improvement, but still disappointing.
One guy on the team was motivated to rewrite the API in Go as a proof of concept, and we were blown away. With the same 1 vCPU it was now able to handle 400 requests per second, while using ~100-200MiB of memory, and having approximately 20% better response times.
> builds just as fast (at least when not using some popular build tools)
I find this a little bit of a cop-out, because almost everyone is using the popular build tools. And it's quite a chore to build a full application without those popular build tools. With Go, all batteries for building are included.
Well, what frameworks were used? Also what is behind the web requests, what were they doing? Because it's comparing mostly frameworks, not languages.
As for the build tools, unfortunately the scene is not the best on Java - but javac itself is indeed fast.
From your description it sounds like you're comparing an old Java program running on an old JDK with a new Go program running on a new Go runtime. These days Java has virtual threads (similar to Go's goroutines) and doesn't need a "reactive stack", and its optimising compiler and GCs blow Go out of the water without breaking a sweat.