Pointers

Like C, go uses pointers. A pointer is used to refer to the address in memory of a variable. You can then use the pointer to refer back to the variable.

package main

import (
	"fmt"
)

func main() {
	x := 1
	p := &x
	fmt.Println(p)  // prints the address
	fmt.Println(*p) // prints the value of what's at that address (1)
	*p = 2          // updates x via the pointer
	fmt.Println(x)
}

/*
Prints the following:
0xc0000b2008
1
2
*/

The & operator returns a variable’s address, a pointer to the variable.

The * operator is used on a pointer to return the value at that address. This is called dereferencing.

The value of a variable that is a pointer is a memory address, something like 0xc0000b2008.

It’s quite common to pass around pointers as arguments to functions, and use this as a method for aggregating values between functions.

If you want a function to mutate a variable, then you write it to accept a pointer type. For example.

// double the value of an integer
func double(i *int) {
  *i += *i
}

TLDR

When you see & in front of a variable, read it as “address of”. When you see * in front of a variable read it as “value at address”.