Welcome to the lesson on Polymorphism with Go. Polymorphism, an essential pillar of object-oriented programming (OOP), enables us to design versatile, legible, and modular code that promotes code reuse. In this lesson, you will understand Polymorphism and its implementation in Go.

The marvel of Polymorphism lies in its ability to treat different data types as identical forms, thus simplifying your code and boosting its extensibility.

Consider the management of a zoo that houses various animals, such as Tigers, Elephants, and Monkeys. Each animal type exhibits specific behaviors but shares common features like eating, thereby demonstrating Polymorphism.

Polymorphism in Go is implemented using Interfaces — a sophisticated collection of method signatures that allow different entities to follow standard interactions.

We demonstrate this with an example featuring the Shape interface and two structs — Circle and Rectangle.

Go
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1package main
2
3import (
4    "fmt"
5    "math"
6)
7
8// Shape interface declaration
9type Shape interface {
10    Area() float64
11}
12
13// Circle struct declaration
14type Circle struct {
15    radius float64
16}
17
18// Rectangle struct declaration
19type Rectangle struct {
20    width, height float64
21}
22
23// Implementing the Area method for Circle
24func (c Circle) Area() float64 {
25    return math.Pi * c.radius * c.radius
26}
27
28// Implementing the Area method for Rectangle
29func (r Rectangle) Area() float64 {
30    return r.width * r.height
31}
32
33func main() {
34    circle := Circle{2}
35    rectangle := Rectangle{3, 4}
36    fmt.Printf("Area of Circle: %f\n", circle.Area())  //prints "Area of Circle: 12.566371"
37    fmt.Printf("Area of Rectangle: %f\n", rectangle.Area()) //prints "Area of Rectangle: 12.000000"
38}

Here, both Circle and Rectangle implement the Area method. Thus, wherever a Shape is expected, a Circle or Rectangle can be used interchangeably.

Let's exemplify Polymorphism using a zoo simulator that houses Dogs, Cats, and Birds. We aim to hear each animal's unique sound.

Go
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1package main
2
3import (
4    "fmt"
5)
6
7// Animal interface declaration
8type Animal interface {
9    Sound() string
10}
11
12// Dog struct declaration
13type Dog struct{}
14
15// Cat struct declaration
16type Cat struct{}
17
18// Bird struct declaration
19type Bird struct{}
20
21// Implementing the Sound method for Dog
22func (d Dog) Sound() string {
23    return "Woof!"
24}
25
26// Implementing the Sound method for Cat
27func (c Cat) Sound() string {
28    return "Meow!"
29}
30
31// Implementing the Sound method for Bird
32func (b Bird) Sound() string {
33    return "Tweet!"
34}
35
36func makeSound(a Animal) {
37    fmt.Println(a.Sound())
38}
39
40func main() {
41    dog := Dog{}
42    cat := Cat{}
43    bird := Bird{}
44    
45    makeSound(dog)    //prints "Woof!"
46    makeSound(cat)    //prints "Meow!"
47    makeSound(bird)   //prints "Tweet!"
48}

Here, the Dog, Cat, and Bird structs implement the Animal interface. This exemplifies Polymorphism, as makeSound works with any Animal and prints the animal's unique sound.

In this lesson, we delved into Polymorphism — an indispensable component of enhancing code flexibility and efficiency. The Interfaces in Go offer a robust mechanism to implement Polymorphism; understanding and using it enhances your programming capabilities.

Now, strengthen your understanding of Polymorphism through relatable real-world scenarios.

Having unveiled the concept of Polymorphism, it's now time to put theory into practice. After the lesson, engage with tailor-made exercises to apply the freshly-gained knowledge. Remember, practice sessions unlock diverse insights into Polymorphism. Embrace the fun of coding with Go!