As I mentioned in my original comment once you start throwing around the expression "low-level language" or "systems language" you invite comparisons to C/C++/Rust.

Thus you will end up with a list of points like this:

It makes less efficient use of hardware due to poor vectorization and lack of JIT to take advantage of this information which would be apparent at runtime. Namely escape analysis would be particularly good. I imagine that Go on Graal would be a very very fast language if time was invested there.

Also until recently generics weren't a thing so it made it impossible to do -high performance- generic data-structures without code-gen. They were possible, but slow as balls due to interface{} and reflection.

It's garbage collector is mediocre for latency, nothing impressive. But it's straight dog shit for throughput. Definitely not -fast- compared to JVM/Hotspot/ZGC.

So, on the good side of Go it provides easy/good access to primitive types and primitive arrays of said types so as long as you know what you are doing you can generally massage the compiler into doing something not completely stupid.

That said if I want to write really fast code in something that isn't C/C++/Rust I would much prefer Java or C#... or more logically if FAST is the primary concern then I would probably pick C++ or Rust.