Go doesn't have a generational & compacting GC (where allocation can be made really efficient: just bumping a pointer), hence heap allocation are expensive in Go (but idk the details, and maybe they're not as expensive as they are in C or Rust).

Then to avoid performance penalties, you need to reduce allocations to the minimum, but since Go use escape analysis to decide whether to allocate on the heap or not, you don't have full control on what is heap-allocated or not, and avoiding allocations can be quite tricky.