When a Go function parameter is passed by value, it means only a copy of the value is accessed and manipulated inside the function. The original value of the variable that is passed as an argument to the function remains intact.

func makeMeOlder(age int) {
  age += 5
}

func main() {
  myAge := 10
  makeMeOlder(myAge)
  fmt.Println(myAge)
  // myAge is still 10
}