Structs

TL;DR

Go does not have classes or objects. Instead, it relies heavily on Structs—typed collections of fields. You can attach methods to structs to simulate object-oriented behavior.

Mental Model

How It Works

A struct groups data together.
To attach behavior (methods) to a struct, you write a normal function but add a Receiver argument right before the function name.

There are two types of receivers:

1. Value Receiver (u User): Operates on a copy of the struct. Cannot modify the original struct.
2. Pointer Receiver (u *User): Operates on a pointer to the struct. Can modify the original struct. This is the most common.

Example

package main

import "fmt"

// 1. Defining the Struct
type User struct {
	Name  string
	Email string
	Age   int
}

// 2. Method with a Pointer Receiver (Can modify the struct)
func (u *User) UpdateEmail(newEmail string) {
	u.Email = newEmail
}

// 3. Method with a Value Receiver (Read-only)
func (u User) GetProfile() string {
	return fmt.Sprintf("%s (%s)", u.Name, u.Email)
}

func main() {
	// Creating an instance
	admin := User{
		Name:  "Alice",
		Email: "alice@example.com",
		Age:   30,
	}

	// Calling methods
	fmt.Println(admin.GetProfile()) // "Alice (alice@example.com)"
	
	admin.UpdateEmail("admin@company.com")
	
	fmt.Println(admin.Email) // "admin@company.com"
}

Common Interview Questions

Does Go support inheritance?

No. Go intentionally omits class inheritance (the extends keyword in Java/TS). Instead, Go encourages Composition. You can embed one struct inside another.

type Logger struct {}
type Server struct {
    Logger // Embedded struct (Composition)
    Port int
}

The Server struct now magically has access to all the methods of Logger.

How do you make a struct field private?

Go uses Exported vs Unexported visibility, which is determined entirely by the capitalization of the first letter.
If a field is Name string, it is exported (public to other packages). If it is name string, it is unexported (private, accessible only within the same package). There are no public or private keywords.