Make sure DelayType function gets consistent values of n

Without this change DelayType function gets n either from
0,1,2,... or from 1,2,3,... depending on the value of Attempts
config value.

This change unifies the behaviour and makes n always take values from
0,1,2,...

Fixes avast#124

Signed-off-by: Piotr Jastrzebski <[email protected]>

retry.go

@@ -156,7 +156,6 @@ func DoWithData[T any](retryableFunc RetryableFuncWithData[T], opts ...Option) (
 			lastErr = err
 
 			config.onRetry(n, err)
-			n++
 			select {
 			case <-config.timer.After(delay(config, n, err)):
 			case <-config.context.Done():
@@ -165,6 +164,7 @@ func DoWithData[T any](retryableFunc RetryableFuncWithData[T], opts ...Option) (
 				}
 				return emptyT, config.context.Err()
 			}
+			n++
 		}
 	}