Lesson 1.2

Variables and Types

Learn how to declare variables, understand Go's type system, and master the basics of working with different data types in Go.

What you'll learn
  • •How to declare and initialize variables in Go
  • •Understanding basic types in Go: integers, floats, strings, and booleans
  • •Type inference and explicit type declarations
  • •Constants and their usage
  • •Zero values and type conversions

Variable Declaration

Go offers several ways to declare variables. The most explicit way uses the var keyword:

var name string = "John"
var age int = 30
var isStudent bool = true

Go can also infer the type from the value, making your code more concise:

var name = "John"    // type inferred as string
var age = 30         // type inferred as int
var isStudent = true // type inferred as bool

Short Variable Declaration

Inside functions, you can use the short declaration operator := which is the most common way to declare variables:

func main() {
    name := "John"
    age := 30
    isStudent := true

    fmt.Println(name, age, isStudent)
}
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Pro tip

The := operator can only be used inside functions. For package-level variables, you must use var.

Basic Types

Go has several built-in types. Here are the most common ones:

Numeric Types
  • int - Platform-dependent integer
  • int8, int16, int32, int64 - Fixed-size integers
  • float32, float64 - Floating-point numbers
Other Basic Types
  • string - Text data
  • bool - true or false
  • byte - Alias for uint8
var count int = 42
var price float64 = 19.99
var message string = "Hello, Go!"
var isActive bool = true

Zero Values

Variables declared without an explicit initial value receive their zero value:

var i int       // 0
var f float64   // 0.0
var b bool      // false
var s string    // "" (empty string)

Practice Exercise

Challenge: Personal Information Program

Create a program that declares variables for personal information and prints them:

  • First name and last name (strings)
  • Age (integer)
  • Height in meters (floating-point number)
  • Whether you are a student (boolean value)

Print all values formatted using fmt.Printf.