No source needed -- you're right. The author's looking in the symbol table, and in 1.16 the Go linker set the size of runtime.pclntab to 0. If the OP used nm to look at their binary, they'd have seen that pclntab is still there. They author has apparently revised their article to address some of this (yet still draw some incorrect conclusions).

(This is derived from Russ' discussion above.)