How do pointers work in Go?

&x gives the address of x, and *p reads or writes the value at that address, so changing *p changes x. A pointer is a variable that stores such an address. The type *int means a pointer to an int, and its zero value is nil. Dereferencing a nil pointer panics at run time.

Go uses pass by value for every argument. Pass a pointer when a function must change the caller's variable, or when copying a large struct costs too much. Go has no pointer arithmetic. The garbage collector keeps a value alive while any pointer to it exists, so returning a pointer to a local variable is safe.

var x int = 42
var p *int = &x  // p points to x

fmt.Println(*p)  // Dereference: prints 42
*p = 21          // Change value through pointer
fmt.Println(x)   // prints 21

// Zero value of pointer is nil
var ptr *int
if ptr == nil {
    fmt.Println("Pointer is nil")
}