Checking of variable implements interface without compiling

I want to know whether a concrete type implements a specefic interface and print it out. I have written an example [0] with a self defined struct (MyPoint) beeing not an interface-type. MyPoint has the function Read as defined in the interface of io.Reader:

type MyPoint struct {
   X, Y int
}

func (pnt *MyPoint) Read(p []byte) (n int, err error) {
    return 42, nil
}

The aim is to get the information that the concrete type p implements the interface io.Writer. Therefore I have written a short main trieng to get a true for the check.

func main() {
     p := MyPoint{1, 2}
}

The first idea was to check it with the help of reflection and a type-switch and adding check(p) to to the main-function.

func checkType(tst interface{}) {
    switch tst.(type) {
    case nil:
        fmt.Printf("nil")
    case *io.Reader:
        fmt.Printf("p is of type io.Reader\n")
    case MyPoint:
        fmt.Printf("p is of type MyPoint\n")
    default:
        fmt.Println("p is unknown.")
    }
}

The output is: p is of type MyPoint. After a bit of research I know that I should have expected that because Go's types are static and therefore the type of p is MyPoint and not io.Reader. In addition to that io.Reader is an interface-type which is different to type MyPoint.

I found one solution e.g. at [1] which checks whether MyPoint can be an io.Reader at compile time. It works.

var _ io.Reader = (*MyPoint)(nil)

But that isn't the solution I wanted. Tries like below fails, too. I think it's because of the reason above, isn't it?

i := interface{}(new(MyPoint))
    if _, ok := i.(io.Reader); ok {
        fmt.Println("i is an io.Reader")
}
pType := reflect.TypeOf(p)
if _, ok := pType.(io.Reader); ok {
    fmt.Println("The type of p is compatible to io.Reader")
}

writerType := reflect.TypeOf((*io.Writer)(nil)).Elem()
fmt.Printf("p impl. Writer %t \n", pType.Implements(writerType))

Exists one solution to check whether p implements the interface without compiling? I hope that someone can help me.

[0] http://ift.tt/1gYepsV

[1] Explanation of checking if value implements interface. Golang