Eduzan / Go Programming Language
Pointers in Go (Golang)
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A pointer is a variable that stores the memory address of another variable. In Go, pointer types look like *int, *string, *MyStruct, etc.
&x→ “address of x”*p→ “value at the address stored in p” (dereference)
Pointers are useful when you want:
- To modify a variable inside a function (pass-by-reference style)
- To avoid copying large structs (performance)
- To share one piece of data across multiple functions safely (with proper synchronization)
package main
import "fmt"
func main() {
num := 60
ptr := &num // ptr stores address of num
fmt.Println("num:", num)
fmt.Println("&num:", &num)
fmt.Println("ptr:", ptr)
fmt.Println("*ptr:", *ptr) // dereference
*ptr = 90 // modify through pointer
fmt.Println("updated num:", num)
}
Uninitialized pointers are nil.
var p *int
fmt.Println(p) // <nil>
You must not dereference nil (*p) — it will panic.
Method 1: Pass a pointer variable
func modifyValue(p *int) {
*p = 1234
}
func main() {
num := 42
ptr := &num
modifyValue(ptr)
fmt.Println(num) // 1234
}
Method 2: Pass address directly
modifyValue(&num)
Using & (address of an existing struct)
type Book struct {
title string
author string
}
func main() {
b := Book{title: "Go Programming", author: "Alice"}
pb := &b
pb.title = "Advanced Go" // auto-dereference for fields
fmt.Println(b.title) // Advanced Go
}
Using new
new(T) allocates zero-value T and returns *T.
type Car struct {
model string
year int
}
func main() {
pc := new(Car)
pc.model = "Tesla Model 3"
pc.year = 2023
}
A pointer can also point to another pointer.
package main
import "fmt"
func main() {
number := 500
p1 := &number
p2 := &p1 // pointer to pointer
fmt.Println(number) // 500
fmt.Println(*p1) // 500
fmt.Println(**p2) // 500
**p2 = 1000
fmt.Println(number) // 1000
}
You can compare pointers using == and !=.
- Two pointers are equal if they point to the same address, or both are nil.
✅ Correct comparison (compare pointer values):
p1 := &a
p2 := &b
p3 := &a
fmt.Println(p1 == p2) // false
fmt.Println(p1 == p3) // true
⚠️ Note: comparing &p1 == &p2 compares the addresses of the pointer variables themselves, not what they point to.
End of lesson.