improved UnreadString

reader.go

@@ -46,8 +46,8 @@ func (r *Reader) UnreadRune() error {
 	return nil
 }
 
-// UnreadString calls UnreadRune for each rune in str
+// UnreadString calls UnreadRune for each rune in str + one addtional rune for the separator rune
-// The actual runes are irrelevant.
+// The actual runes in str are irrelevant.
 // Only the rune count of str determines the amount of UnreadRune calls.
 // The first error occured will be returned immediately.
 func (r *Reader) UnreadString(str string) error {
@@ -57,7 +57,7 @@ func (r *Reader) UnreadString(str string) error {
 			return err
 		}
 	}
-	return nil
+	return r.UnreadRune()
 }
 
 // StringWhile reads runes and calls f for each one.