https://learnku.com/courses/go-api/1.17
$ go run main.go
# golang.org/x/sys/unix
../../go/pkg/mod/golang.org/x/sys@v0.0.0-20200116001909-b77594299b42/unix/syscall_darwin.1_13.go:25:3: //go:linkname must refer to declared function or variable
../../go/pkg/mod/golang.org/x/sys@v0.0.0-20200116001909-b77594299b42/unix/zsyscall_darwin_amd64.1_13.go:27:3: //go:linkname must refer to declared function or variable
../../go/pkg/mod/golang.org/x/sys@v0.0.0-20200116001909-b77594299b42/unix/zsyscall_darwin_amd64.1_13.go:40:3: //go:linkname must refer to declared function or variable
go get -u golang.org/x/sys