refactor: lucky number exercises

* guess < 0 doesn't check for definitive positivity
* n := rand.Intn(guess + 1) may pick 0, a non positive integer
* remove: redundant parentheses from the loop in 06-dynamic-difficulty

13-loops/exercises/08-lucky-number-exercises/04-verbose-mode/solution/main.go

@@ -53,13 +53,13 @@ func main() {
 		return
 	}
 
-	if guess < 0 {
+	if guess <= 0 {
 		fmt.Println("Please pick a positive number.")
 		return
 	}
 
 	for turn := 1; turn <= maxTurns; turn++ {
-		n := rand.Intn(guess + 1)
+		n := rand.Intn(guess) + 1
 
 		if verbose {
 			fmt.Printf("%d ", n)