Struct

In Go, a struct is a collection of fields. Each field has a name and a type. Fields are also known as members of a struct. A struct can be defined using the struct keyword, followed by a list of fields enclosed in curly braces. Here's an example of a struct that represents a rectangle:

type Rectangle struct {
    width  float64
    height float64
}

You can create a new instance of a struct by using the new keyword, or by initializing the fields directly. Here's an example of both:

// using the new keyword
r := new(Rectangle)

// initializing fields directly
r := Rectangle{width: 10, height: 20}

You can also create a struct using a struct literal, which is similar to an object literal in JavaScript. Here's an example:

r := Rectangle{10, 20}

You can access the fields of a struct using dot notation. For example, you can get the width of a rectangle by calling r.width. You can also change the values of the fields by assigning a new value to them. Here's an example:

// getting the width of a rectangle
fmt.Println(r.width)

// changing the value of the width field
r.width = 15

It is also possible to define methods on structs, which are functions that operate on the struct's fields. Here's an example of a method that calculates the area of a rectangle:

func (r *Rectangle) Area() float64 {
    return r.width * r.height
}

You can call this method by using the dot notation on an instance of the struct, like this:

area := r.Area()

It is also possible to define a function that takes a struct as an argument, like this:

func doubleWidth(r *Rectangle) {
    r.width = r.width * 2
}

You can call this function and pass an instance of the struct as an argument, like this:

doubleWidth(&r)

You can also define a struct that has another struct as one of its fields, which is called a nested struct or embedded struct

type Person struct {
    Name string
    Age  int
}

type Employee struct {
    Person
    Salary int
}

You can use an embedded struct to access its fields without needing to use the dot notation.

e := Employee{Person{"John", 30}, 5000}
fmt.Println(e.Name, e.Age, e.Salary)