func main() {
sl := make([]*int, 5)
var a int = 5
sl[1] = &a
C.plusOne((**C.int)((unsafe.Pointer)(&sl[0])))
fmt.Println(sl[0])
}
func main() {
f := &C.struct_Foo{}
f.a = 5
f.p = (*C.int)((unsafe.Pointer)(new(int)))
C.plusOne(&f.a)
fmt.Println(int(f.a))
}