Loops

Go keeps loops simple on purpose by having only one loop keyword, for, which can still be used in several different ways.

Variants

• Classic loop:

  for i := 0; i < 5; i++ {
      fmt.Println(i)
  }
  
  // 0
  // 1
  // 2
  // 3
  // 4

• While loop:

  i := 0
  for i < 5 {
      fmt.Println(i)
      i++
  }
  
  // 0
  // 1
  // 2
  // 3
  // 4

• Infinite loop:

  for {
      fmt.Println("running")
  }
  
  // running
  // running
  // running
  // running
  // ... (infinite)

• Range loop:

  Used to loop over integers, strings (runes), arrays, slices, maps, and channels.

  for i := range 3 {
      fmt.Println(i)
  }
  
  // 0
  // 1
  // 2

  nums := []int{10, 20, 30}
  
  for i, v := range nums {
      fmt.Println(i, v)
  }
  
  // 0 10
  // 1 20
  // 2 30

Control Keywords

• break: Stops the loop completely.

  for i := 0; i < 5; i++ {
      if i == 2 {
          break
      }
  
      fmt.Println(i)
  }
  
  // 0
  // 1

• continue: Skips to the next iteration.

  for i := 0; i < 5; i++ {
      if i == 2 {
          continue
      }
  
      fmt.Println(i)
  }
  
  // 0
  // 1
  // 3
  // 4

Labeled Loops

A labeled loop is a loop with a name that lets break or continue target a specific loop when loops are nested.

outerLoop:
    for i := 0; i < 3; i++ {
        for j := 0; j < 3; j++ {
            if i == j {
                continue outerLoop
            }

            fmt.Println(i, j)
        }
    }

// 1 0
// 2 0
// 2 1