Go源代码中的报表覆盖率在哪里增加了语句计数器?

I am looking into the Golang source code and want to understand how does it calculate coverage. I understand that each block of code has it's own statement counter; however, where is that statement counter being incremented? Here is a link for the cover.go: https://github.com/golang/go/blob/master/src/cmd/cover/cover.go

Realized that you are unable to see where the counters are incremented;; the counters are boolean statements at the end of each block of code and are set to true/false during buildtime.