Explain the use of Go's interfaces and polymorphism for defining and using abstract types and behaviors in Go programs?

In Go, an interface is a collection of method signatures that define a set of behaviors that a type must implement to be considered as implementing the interface. Interfaces provide a way to define abstract types and behaviors without specifying the concrete implementation. They allow for polymorphism, which is the ability to use values of different types as if they were of the same type, as long as they implement the same set of behaviors defined by an interface.

Here's an example:

type Shape interface {
    Area() float64
    Perimeter() float64

type Rectangle struct {
    Width  float64
    Height float64

func (r Rectangle) Area() float64 {
    return r.Width * r.Height

func (r Rectangle) Perimeter() float64 {
    return 2*r.Width + 2*r.Height

func PrintShapeInfo(s Shape) {
    fmt.Printf("Area: %v, Perimeter: %v\n", s.Area(), s.Perimeter())

func main() {
    r := Rectangle{Width: 3, Height: 4}

In this example, we define an interface **Shape** with two methods: **Area()** and **Perimeter()**. We also define a concrete type **Rectangle** with **Width** and **Height** fields, and two methods that implement the Shape interface: **Area()** and **Perimeter()**.

The **PrintShapeInfo()** function takes a parameter of type **Shape**, which means it can take any type that implements the **Shape** interface. In the **main()** function, we create a **Rectangle** value and pass it to the **PrintShapeInfo()** function. Even though **Rectangle** is a concrete type and not an interface, we can still pass it as a parameter because it implements the **Shape** interface.

This is an example of polymorphism in Go, where we can use different types as if they were the same type as long as they implement the same set of behaviors defined by an interface.

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