Go — Variables

Variable declaration

package main

import "fmt"

func main() {
    // var declaration
    var name string = "Alice"
    var age int = 30

    // Type inference
    var city = "NYC" // inferred as string

    // Short declaration (inside functions only)
    score := 95

    fmt.Println(name, age, city, score)
}

Zero values

When declared without initialization, variables get zero values:

var i int       // 0
var f float64   // 0.0
var b bool      // false
var s string    // ""
var p *int      // nil

Multiple declarations

var (
    x int    = 10
    y string = "hello"
    z bool   = true
)

// Short declaration multiple
a, b, c := 1, 2, 3

Scope

package main

import "fmt"

var globalVar = "I am global"

func main() {
    localVar := "I am local"

    {
        blockVar := "I am block-scoped"
        fmt.Println(blockVar)
    }
    // blockVar is not accessible here

    fmt.Println(globalVar)
    fmt.Println(localVar)
}

iota

Generate a sequence of constants:

const (
    Sunday = iota // 0
    Monday        // 1
    Tuesday       // 2
    Wednesday     // 3
    Thursday      // 4
    Friday        // 5
    Saturday      // 6
)

// Bit shifting with iota
const (
    _  = iota
    KB = 1 << (10 * iota) // 1024
    MB                    // 1048576
    GB                    // 1073741824
)

Type inference

Go infers types automatically:

x := 42          // int
y := 3.14        // float64
z := "hello"     // string
b := true        // bool
nums := []int{1, 2, 3} // []int

// Explicit type when needed
var pi float32 = 3.14
var count int64 = 100

Pointer variables

package main

import "fmt"

func main() {
    x := 10
    p := &x    // p is *int, points to x

    fmt.Println(*p)  // 10 (dereference)
    *p = 20           // modify x through pointer
    fmt.Println(x)    // 20
}

Unused variables

Go does not allow unused variables:

// This will NOT compile:
func main() {
    x := 10 // Error: x declared but not used
}

// Use blank identifier to ignore:
func main() {
    _ = 10 // OK
}

Best practices

• Use := for short, clear declarations
• Use var for package-level or zero-value declarations
• Keep variables close to where they're used
• Prefer value types over pointers when possible
• Use meaningful names, avoid single-letter except in loops

Mini Practice

Write Go code that:

1. Declares variables with var and :=
2. Demonstrates zero values
3. Uses iota for a sequence of constants
4. Shows pointer variable usage

Up Next

In the next lesson, you'll learn about Constants — defining fixed values in Go.