goyacc-sample

As of 1.8, 'go tool yacc' is no longer included. Instead, obtain 'goyacc' with the following:
go get -u golang.org/x/tools/cmd/goyacc

Followed by:
goyacc -o calc.go -p Calc calc.y

References:

https://github.com/golang-samples/yacc/tree/master/simple
https://godoc.org/github.com/cznic/goyacc
https://blog.golang.org/generate (outdated)