func main() {
  defer func() {
    if r := recover(); r != nil {
      fmt.Println("Recovered:", r)
    }
  }()

  defer fmt.Println("1")
  defer fmt.Println("2")

  panic("something went wrong")
}

const (
  iterations = 1000000
  addedChar  = "g"
)

func concatWithPlus(n int) string {
  var s string
  for i := 0; i < n; i++ {
    s += addedChar
  }
  return s
}

func concatWithBuilder(n int) string {
  var sb strings.Builder
  sb.Grow(n)
  for i := 0; i < n; i++ {
    sb.WriteString(addedChar)
  }
  return sb.String()
}

func main() {
  // Замерим время для '+'
  start := time.Now()
  concatWithPlus(iterations)
  elapsedPlus := time.Since(start)

  // Замерим время для Builder
  start = time.Now()
  concatWithBuilder(iterations)
  elapsedBuilder := time.Since(start)

  fmt.Printf("Конкатенация с '+': %v\n", elapsedPlus)
  fmt.Printf("Конкатенация с Builder: %v\n", elapsedBuilder)
}

const (
  zero = iota // 0
  one         // 1
  two         // 2
)

const (
  three = iota + 3 // 3
  four             // 4
)

const (
  // Удобная история для масок
  ReadPermission    = 1 << iota // 1 << 0 = 1 (00000001)
  WritePermission               // 1 << 1 = 2 (00000010)
  ExecutePermission             // 1 << 2 = 4 (00000100)
)