修改参数类型

为了保持向后兼容，

@@ -157,7 +157,17 @@ func (e *Email) Bytes() ([]byte, error) {
 }
 
 // Add attach file to the send mail
-func (e *Email) AttachFile(filename string, id string) (a *Attachment, err error) {
+func (e *Email) AttachFile(args ...string) (a *Attachment, err error) {
+	argsLength := len(args)
+	if argsLength < 1 || argsLength > 2 {
+		return
+	}
+	filename := args[0]
+	id := ""
+	if argsLength > 1 {
+		id = args[1]
+	}
+	id = args[1]
 	f, err := os.Open(filename)
 	if err != nil {
 		return
@@ -169,7 +179,18 @@ func (e *Email) AttachFile(filename string, id string) (a *Attachment, err error
 
 // Attach is used to attach content from an io.Reader to the email.
 // Parameters include an io.Reader, the desired filename for the attachment, and the Content-Type.
-func (e *Email) Attach(r io.Reader, filename string, c string, id string) (a *Attachment, err error) {
+func (e *Email) Attach(r io.Reader, filename string, ci ...string) (a *Attachment, err error) {
+	args := ci
+	argsLength := len(args)
+	if argsLength < 1 || argsLength > 2 {
+		return
+	}
+	c := args[0]
+	id := ""
+	if argsLength > 1 {
+		id = args[1]
+	}
+	id = args[1]
 	var buffer bytes.Buffer
 	if _, err = io.Copy(&buffer, r); err != nil {
 		return
@@ -189,7 +210,7 @@ func (e *Email) Attach(r io.Reader, filename string, c string, id string) (a *At
 	if id != "" {
 		at.Header.Set("Content-Disposition", fmt.Sprintf("inline;\r\n filename=\"%s\"", filename))
 		at.Header.Set("Content-ID", fmt.Sprintf("<%s>", id))
-	}else {
+	} else {
 		at.Header.Set("Content-Disposition", fmt.Sprintf("attachment;\r\n filename=\"%s\"", filename))
 	}
 	at.Header.Set("Content-Transfer-Encoding", "base64")