How are arguments passed to a function — by value or by reference?

In Go, function arguments are passed by value. This means that when calling a function, a copy of the value is passed to the function's parameter.

However, if a pointer is passed, then the value of the pointer (which points to the original data) is copied. This allows indirect modification of the data the pointer points to.

Example:

func increment(val int) {
    val++
}

func incrementPointer(val *int) {
    (*val)++
}

func main() {
    a := 5
    increment(a)          // a remains 5
    incrementPointer(&a)  // a becomes 6
}

In summary: basic types are passed by value, but pointers can be used to modify the original data.