go - Why isn't my Stringer interface method getting invoked? When using fmt.Println

Question

Suppose I have the following code:

package main

import "fmt"

type Car struct{
    year int
    make string
}

func (c *Car)String() string{
    return fmt.Sprintf("{make:%s, year:%d}", c.make, c.year)
}

func main() {
    myCar := Car{year:1996, make:"Toyota"}
    fmt.Println(myCar)
}

When I call fmt.Println(myCar) and the object in question is a pointer, my String() method gets called properly. If, however the object is a value, my output is formatted using the default formatting built into Go and my code to format the said object is not called.

The interesting thing is in either case if I call myCar.String() manually it works properly whether my object is either a pointer or value.

How can I get my object formatted the way I want no matter if the object is value-based or pointer-based when used with Println?

I don't want to use a value method for String because then that means every time it's invoked the object is copied which seams unreasonable. And I don't want to have to always manually called .String() either because I'm trying to let the duck-typing system do it's work.

Answer 1

Waitting for answers