Simple example to see functions, methods, methods with variable arguments

package main

import "fmt"

type Hours int

// function
func Increment(h Hours) Hours {
  return (h + 1) % 24
}

// method with no arguments (pass by value)
func (h Hours) IncrementMethod() {
  return (h + 1) % 24  // return value aka return copy of original
}

// method with pointer no arguments (pass by reference)
func (h *Hours) IncrementMethod() {
  *h = (*h + 1) % 24  // update value aka mutate orignal in memory
}

// method with single argument
func (h *Hours) IncrementByX(x Hours) {
  *h = (*h + x) % 24
}

// method with variable arguments 
func (h *Hours) IncrementBySeveral(x ...Hours) {
  sum := Hours(0)
  for i := range x {  // come in array, so iterate
    sum += x[i]
  }
  *h = (*h + sum) % 24
}

func main() {

  // as function
  hours1 := Hours(23)
  hours1 = Increment(hours1)
  fmt.Println(hours1) // Prints "0".

  // as method
  hours2 := Hours(23)
  hours2.IncrementMethod()
  fmt.Println(hours2) // Prints "0"

  // as method with parameter
  hours3 := Hours(23)
  hours3.IncrementByX(5)
  fmt.Println(hours3) // Prints "4"

  // as method with variable amount of arguments
  hours4 := Hours(23)
  hours4.IncrementBySeveral(3, 5)
  fmt.Println(hours4) // Prints "7"
}