It's actually not that hard to beat. Quarkus proved that it's way better than Spring Boot in a lot of aspects based on open standards and battle tested frameworks like Vertx. Also on Quarkus you can use in parallel blocking and non-blocking IO and also high level declarative routes with annotations to lower lever vertx routes and handlers.
Java or Kotlin seems actually a very good compromise. Very good performance and also actually in the top of the list of the energy efficient languages. Plus you can find a lot of more devs using JVM tech stack.
I would not choose Go, the language is simply to simple and not modern at all. You will still have to check for nil values ( see Kotlin, Swift for alternative) or you have to use old for loops to manipulate cumbersome collections types like slices instead of having functional paradigms build into the language ( again Kotlin, Swift, Java Streams etc). A good alternative if already using JVM would be some of the newer generation frameworks like Quarkus (https://quarkus.io), Helidon etc
I would not agree that Go is a good replacement for Java Microservices. I would suggest looking into something like Quarkus (https://quarkus.io) and if Java is to verbose for someone, she/he can checkout Kotlin (https://kotlinlang.org) which is 100% interoperable with Java but clean, modern and pragmatic. With Quarkus you have a very powerful but simple framework that out of the box (GraalVM) can be compiled also to a single binary if you need very fast startup and very low memory consumption.
Go evangelises simplicity but when someone has to use it in a bigger project the lang is very cumbersome. You don't have any functional programming features like filter, map, find to manipulate collections. The not null (nil) safety or the magic with interfaces{} does it make non safe especially compared to modern languages like Kotlin,Swift which have the notion of nullability build in the language itself. Dependency Injection support is very limited. I think Go is hyped because of the excellent single binary feature which you have nowadays via GraalVM also for Java, Kotlin as I described above.