Like sync.Once but with errors

once.go

// OnceNoError is like sync.Once but retries until no error occured.
type OnceNoError struct {
	mu   sync.Mutex
	done uint32
}

func (once *OnceNoError) Do(fn func() error) (err error) {
	if atomic.LoadUint32(&once.done) == 1 {
		return
	}
	once.mu.Lock()
	defer once.mu.Unlock()
	if once.done == 0 {
		defer func() {
			if err == nil {
				atomic.StoreUint32(&once.done, 1)
			}
		}()
		err = fn()
	}
	return
}