return scanner errors

day-02/internal/one/solve.go

@@ -12,12 +12,15 @@ type comparator func([]int, int) bool
 
 func Solve(data []byte) (int, error) {
 	r := bytes.NewReader(data)
-	sum := parseLines(r)
+	sum, err := parseLines(r)
+	if err != nil {
+		return 0, err
+	}
 
 	return sum, nil
 }
 
-func parseLines(r io.Reader) int {
+func parseLines(r io.Reader) (int, error) {
 	var sum int
 
 	scanner := bufio.NewScanner(r)
@@ -29,5 +32,9 @@ func parseLines(r io.Reader) int {
 		}
 	}
 
-	return sum
+	if err := scanner.Err(); err != nil {
+		return 0, err
+	}
+
+	return sum, nil
 }