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Core - Math helpers

This page lists all retry operations available in the core package of lo.

• Attempt

  retrycore

  🧩 Source📚 GoDoc🎮 Try on Go Playground

  Invokes a function up to N times until it returns nil. Returns the number of iterations attempted (1-based) and the last error. Useful for retrying operations that might fail temporarily.

  // Success after 3 attempts
  iter, err := lo.Attempt(5, func(i int) error {
      if i == 2 {
          return nil // succeeds on 3rd attempt (index 2)
      }
      return errors.New("failed")
  })
  // iter: 3, err: nil

  // All attempts fail - returns last error
  iter, err = lo.Attempt(3, func(i int) error {
      return fmt.Errorf("attempt %d failed", i)
  })
  // iter: 3, err: "attempt 2 failed" (last error from index 2)

  // Immediate success on first attempt
  iter, err = lo.Attempt(5, func(i int) error {
      return nil // succeeds immediately
  })
  // iter: 1, err: nil

  // Zero attempts - returns error without calling function
  iter, err = lo.Attempt(0, func(i int) error {
      return errors.New("should not be called")
  })
  // iter: 0, err: "maxIteration must be greater than 0"

  Similar:

  attemptwhileattemptwhilewithdelayattemptwithdelay

  Prototype:

  func Attempt(maxIteration int, f func(index int) error) (int, error)

• AttemptWithDelay

  retrycore

  🧩 Source📚 GoDoc🎮 Try on Go Playground

  Invokes a function up to N times with a pause between calls until it returns nil. Returns iterations, elapsed, and error.

  iter, dur, err := lo.AttemptWithDelay(
      3,
      100*time.Millisecond,
      func(i int, d time.Duration) error {
          if i == 1 {
              return nil
          }
          return errors.New("x")
      },
  )

  Similar:

  attemptattemptwhileattemptwhilewithdelay

  Prototype:

  func AttemptWithDelay(maxIteration int, delay time.Duration, f func(index int, duration time.Duration) error) (int, time.Duration, error)

• AttemptWhile

  retrycore

  🧩 Source📚 GoDoc🎮 Try on Go Playground

  Invokes a function up to N times until it returns nil. The second return value controls whether to continue attempting.

  count, err := lo.AttemptWhile(5, func(i int) (error, bool) {
      if i == 2 {
          return nil, false
      }
      return errors.New("fail"), true
  })
  // count == 3, err == nil

  Similar:

  attemptattemptwhilewithdelayattemptwithdelay

  Prototype:

  func AttemptWhile(maxIteration int, f func(int) (error, bool)) (int, error)

• AttemptWhileWithDelay

  retrycore

  🧩 Source📚 GoDoc🎮 Try on Go Playground

  Like AttemptWhile, but pauses between attempts and returns elapsed time.

  count, dur, err := lo.AttemptWhileWithDelay(
      5,
      time.Millisecond,
      func(i int, d time.Duration) (error, bool) {
          return errors.New("x"), i < 1
      },
  )

  Similar:

  attemptattemptwhileattemptwithdelay

  Prototype:

  func AttemptWhileWithDelay(maxIteration int, delay time.Duration, f func(int, time.Duration) (error, bool)) (int, time.Duration, error)