fixed StringWhile

reader.go

@@ -84,8 +84,9 @@ func (r *Reader) UnreadString(str string) error {
 func (r *Reader) StringWhile(f func(rn rune) bool) (string, error) {
 	s := new(strings.Builder)
 
+	var rn rune
 	var err error
-	for rn, err := r.Rune(); err == nil && f(rn); rn, err = r.Rune() {
+	for rn, err = r.Rune(); err == nil && f(rn); rn, err = r.Rune() {
 		s.WriteRune(rn)
 	}
 

reader_test.go

@@ -22,3 +22,15 @@ func TestPos(t *testing.T) {
 		}
 	}
 }
+
+func TestEOF(t *testing.T) {
+	r := NewReader(strings.NewReader("hello world\nasddsa"))
+
+	for line, err := r.StringUntil(isNewline); err == nil; line, err = r.StringUntil(isNewline) {
+		fmt.Println(line, err)
+	}
+}
+
+func isNewline(rn rune) bool {
+	return rn == '\n'
+}