Explain the concept of interfaces in Go and how they promote code reusability.

In Go, interfaces play a crucial role in promoting code reusability and enabling polymorphism. They provide a way to define a set of method signatures that a type can implement. By adhering to the defined interface, a type automatically satisfies the contract specified by the interface. Let's delve into the concept of interfaces in Go and their role in code reusability:

1. Interface Definition:

* An interface in Go is a collection of method signatures defined as a named type.
* Syntax: `type InterfaceName interface { Method1() returnType1 Method2() returnType2 ... }`
* Interfaces specify what methods a type must have to satisfy the interface, but they do not provide any implementation details.
2. Interface Implementation:

* Any type that implements all the methods declared in an interface implicitly satisfies that interface.
* There is no explicit declaration or inheritance required. It is purely based on method signature matching.
* This allows different types to be used interchangeably based on their shared behavior defined by the interface.
* Example:
```
go`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 + r.height)
}`
```
3. Interface as a Contract:

* Interfaces serve as contracts or agreements between code components.
* When a type satisfies an interface, it guarantees that it provides the methods specified by the interface.
* This allows other parts of the codebase to rely on the expected behavior without depending on specific implementations.
* It promotes loose coupling and enables code reuse and extensibility.
4. Polymorphism and Code Reusability:

* Interfaces in Go enable polymorphism, which allows objects of different types to be treated uniformly based on their shared behavior defined by the interface.
* This promotes code reusability by writing generic code that can work with different types as long as they satisfy the required interface.
* It allows for writing flexible and modular code where implementations can be easily swapped and extended.
* Example:
```
go`func PrintArea(shape Shape) {
fmt.Println("Area:", shape.Area())
}

func main() {
rect := Rectangle{width: 5, height: 3}
PrintArea(rect) // Can pass Rectangle because it satisfies the Shape interface
}`
```
5. Interface Composition:

* Go supports interface composition, where an interface can include other interfaces as part of its definition.
* This allows interfaces to build on top of existing interfaces, combining their methods and defining additional behavior.
* Example:
```
go`type Reader interface {
Read() ([]byte, error)
}

type Writer interface {
Write([]byte) (int, error)
}

type ReadWriter interface {
Reader
Writer
}`
```

Interfaces in Go provide a powerful mechanism for defining contracts and promoting code reusability. They enable polymorphism, allowing objects of different types to be used interchangeably based on shared behavior. By leveraging interfaces, developers can write modular, extensible, and flexible code that can be easily adapted and reused across different parts of the codebase.