New constant iota for contentType html or plain

Delete priorities array and string function, not used and unnecessary
SetBody and AddAlternative require contentType type contentType instead a string (this change break your code, update it)
Update readme
Update example_test.go
Update comment header.go
encoding and encryption constant have function string() private instead String. Changes made on other files like message.go

README.md

@@ -6,7 +6,10 @@ The best way to send emails in Go with SMTP Keep Alive and Timeout for Connect a
 [![Go Report](https://goreportcard.com/badge/github.com/xhit/go-simple-mail)](https://goreportcard.com/report/github.com/xhit/go-simple-mail)
 
 **IMPORTANT**
-This example is for version 2.1.3 and above, for v2.0.0 example go here https://gist.github.com/xhit/54516917473420a8db1b6fff68a21c99
+This example is for version 2.2.0 and above. 
+
+Version 2.1.3 and below use "text/html" and "text/plain" in SetBody and AddAlternative
+Also 2.0.0 and below go to this doc https://gist.github.com/xhit/54516917473420a8db1b6fff68a21c99
 
 # Introduction
 
@@ -19,7 +22,13 @@ is easy to implement other methods for sending emails using a local Postfix, an
 ## Features
 
 Go Simple Mail supports:
-- Attachments
+- Multiple Attachments with path
+- Multiple Attachments in base64
+- Multiple Recipients
+- Priority
+- Reply to
+- Set other sender
+- Set other from
 - Embedded images
 - HTML and text templates
 - Automatic encoding of special characters
@@ -28,6 +37,15 @@ Go Simple Mail supports:
 - Sending multiple emails with the same SMTP connection (Keep Alive or Persistent Connection)
 - Timeout for connect to a SMTP Server
 - Timeout for send an email
+- Return Path
+- Alternaive Email Body
+- CC and BCC
+- Add Custom Headers in Message
+- Send NOOP, RESET, QUIT and CLOSE to SMTP client
+
+## Documentation
+
+https://godoc.org/github.com/xhit/go-simple-mail
 
 ## Download
 
@@ -93,7 +111,7 @@ func main() {
 		AddCc("otherto@example.com").
 		SetSubject("New Go Email")
 
-	email.SetBody("text/html", htmlBody)
+	email.SetBody(mail.TextHTML, htmlBody)
 
 	email.AddInline("/path/to/image.png", "Gopher.png")
 
@@ -124,7 +142,7 @@ func main() {
 			AddTo(to).
 			SetSubject("New Go Email")
 
-		email.SetBody("text/html", htmlBody)
+		email.SetBody(mail.TextHTML, htmlBody)
 
 		email.AddInline("/path/to/image.png", "Gopher.png")
 

email.go

@@ -78,7 +78,7 @@ const (
 
 var encryptionTypes = [...]string{"TLS", "SSL", "None"}
 
-func (encryption encryption) String() string {
+func (encryption encryption) string() string {
 	return encryptionTypes[encryption]
 }
 
@@ -95,10 +95,25 @@ const (
 
 var encodingTypes = [...]string{"quoted-printable", "base64", "binary"}
 
-func (encoding encoding) String() string {
+func (encoding encoding) string() string {
 	return encodingTypes[encoding]
 }
 
+type contentType int
+
+const (
+	// TextHTML sets body type to text/html in message body
+	TextHTML contentType = iota
+	// TextPlain sets body type to text/plain in message body
+	TextPlain
+)
+
+var contentTypes = [...]string{"text/html", "text/plain"}
+
+func (contentType contentType) string() string {
+	return contentTypes[contentType]
+}
+
 // NewMSG creates a new email. It uses UTF-8 by default.
 func NewMSG() *Email {
 	email := &Email{
@@ -309,12 +324,6 @@ const (
 	PriorityLow
 )
 
-var priorities = [...]string{"High", "Low"}
-
-func (priority priority) String() string {
-	return priorities[priority]
-}
-
 // SetPriority sets the email message priority. Use with
 // either "High" or "Low".
 func (email *Email) SetPriority(priority priority) *Email {
@@ -376,14 +385,14 @@ func (email *Email) SetSubject(subject string) *Email {
 }
 
 // SetBody sets the body of the email message.
-func (email *Email) SetBody(contentType, body string) *Email {
+func (email *Email) SetBody(contentType contentType, body string) *Email {
 	if email.Error != nil {
 		return email
 	}
 
 	email.parts = []part{
 		{
-			contentType: contentType,
+			contentType: contentType.string(),
 			body:        bytes.NewBufferString(body),
 		},
 	}
@@ -448,14 +457,14 @@ func (email *Email) AddHeaders(headers textproto.MIMEHeader) *Email {
 // of the email message. This is most commonly used to add an
 // html version in addition to a plain text version that was
 // already added with SetBody.
-func (email *Email) AddAlternative(contentType, body string) *Email {
+func (email *Email) AddAlternative(contentType contentType, body string) *Email {
 	if email.Error != nil {
 		return email
 	}
 
 	email.parts = append(email.parts,
 		part{
-			contentType: contentType,
+			contentType: contentType.string(),
 			body:        bytes.NewBufferString(body),
 		},
 	)
@@ -675,7 +684,7 @@ func dial(host string, port string, encryption encryption, config *tls.Config) (
 	}
 
 	if err != nil {
-		return nil, errors.New("Mail Error on dailing with encryption type " + encryption.String() + ": " + err.Error())
+		return nil, errors.New("Mail Error on dailing with encryption type " + encryption.string() + ": " + err.Error())
 	}
 
 	c, err := newClient(conn, host)

example_test.go

@@ -65,8 +65,8 @@ func TestSendMail(t *testing.T) {
 		AddTo("admin@example.com").
 		SetSubject("New Go Email")
 
-	email.SetBody("text/html", htmlBody)
-	email.AddAlternative("text/plain", "Hello Gophers!")
+	email.SetBody(TextHTML, htmlBody)
+	email.AddAlternative(TextPlain, "Hello Gophers!")
 
 	//Some additional options to send
 	email.SetSender("xhit@test.com")
@@ -149,7 +149,7 @@ func sendEmail(htmlBody string, to string, smtpClient *SMTPClient) error {
 
 	//Get from each mail
 	email.getFrom()
-	email.SetBody("text/html", htmlBody)
+	email.SetBody(TextHTML, htmlBody)
 
 	//Send with high priority
 	email.SetPriority(PriorityHigh)
@@ -160,20 +160,6 @@ func sendEmail(htmlBody string, to string, smtpClient *SMTPClient) error {
 	return err
 }
 
-func TestPriority(t *testing.T) {
-	str := PriorityLow.String()
-
-	if len(str) < 1 {
-		t.Error("Expected Low, returned empty string")
-	}
-
-	str = PriorityHigh.String()
-
-	if len(str) < 1 {
-		t.Error("Expected High, returned empty string")
-	}
-}
-
 //TestWithTLS using gmail port 587
 func TestWithTLS(t *testing.T) {
 	client := NewSMTPClient()

header.go

@@ -1,4 +1,6 @@
-// Package mail implements "Q" encoding as specified by RFC 2047.
+// headers.go implements "Q" encoding as specified by RFC 2047.
+//Modified from https://github.com/joegrasse/mime to use with Go Simple Mail
+
 package mail
 
 import (

message.go

@@ -220,7 +220,7 @@ func (msg *message) addBody(contentType string, body []byte) {
 
 	header := make(textproto.MIMEHeader)
 	header.Set("Content-Type", contentType+"; charset="+msg.charset)
-	header.Set("Content-Transfer-Encoding", msg.encoding.String())
+	header.Set("Content-Transfer-Encoding", msg.encoding.string())
 	msg.write(header, body, msg.encoding)
 }
 
@@ -235,7 +235,7 @@ func (msg *message) addFiles(files []*file, inline bool) {
 	for _, file := range files {
 		header := make(textproto.MIMEHeader)
 		header.Set("Content-Type", file.mimeType+";\n \tname=\""+encodeHeader(escapeQuotes(file.filename), msg.charset, 6)+`"`)
-		header.Set("Content-Transfer-Encoding", encoding.String())
+		header.Set("Content-Transfer-Encoding", encoding.string())
 		if inline {
 			header.Set("Content-Disposition", "inline;\n \tfilename=\""+encodeHeader(escapeQuotes(file.filename), msg.charset, 10)+`"`)
 			header.Set("Content-ID", "<"+msg.getCID(file.filename)+">")