The documentation for SetFinalizer uses named variables obj and finalizer in the method signature, but refers to x and f in the documentation comment. This makes it harder to read, since the doc refers to hypothetical variables rather than the ones used by the function.

Additionally, later down in the comment obj:

It is not guaranteed that a finalizer will run if the size of *obj is zero bytes.

I believe this already tricky method would be easier to understand if the doc used consistent terminology.