Sending an email with Go through AWS SES - amazon-web-services

Question

I wrote a lambda function in Go that would handle a form submission and send an email with the captured form data to a configured email address.
I am using AWS SES, or trying to.
My emailService.go has the following code:
package aj
import (
"bytes"
"context"
"encoding/base64"
"fmt"
"io/ioutil"
"mime/multipart"
"net/http"
"net/smtp"
"os"
"path/filepath"
"strings"
"go.uber.org/zap"
)
var (
host = os.Getenv("EMAIL_HOST")
username = os.Getenv("EMAIL_USERNAME")
password = os.Getenv("EMAIL_PASSWORD")
portNumber = os.Getenv("EMAIL_PORT")
from = os.Getenv("SOURCE_EMAIL")
)
type EmailService struct {
auth smtp.Auth
}
type EmailSender interface {
SendEmail(logger *zap.Logger, ctx context.Context, m *Message) error
}
func NewEmailService() *EmailService {
auth := smtp.PlainAuth("", username, password, host)
return &EmailService{auth}
}
func (s *EmailService) SendEmail(logger *zap.Logger, ctx context.Context, m *Message) error {
return smtp.SendMail(fmt.Sprintf("%s:%s", host, portNumber), s.auth, from, m.To, m.ToBytes())
}
func NewMessage(s, b string) *Message {
return &Message{Subject: s, Body: b, Attachments: make(map[string][]byte)}
}
func (m *Message) AttachFile(src string) error {
b, err := ioutil.ReadFile(src)
if err != nil {
return err
}
_, fileName := filepath.Split(src)
m.Attachments[fileName] = b
return nil
}
func (m *Message) ToBytes() []byte {
buf := bytes.NewBuffer(nil)
withAttachments := len(m.Attachments) > 0
buf.WriteString(fmt.Sprintf("Subject: %s\n", m.Subject))
buf.WriteString(fmt.Sprintf("To: %s\n", strings.Join(m.To, ",")))
if len(m.CC) > 0 {
buf.WriteString(fmt.Sprintf("Cc: %s\n", strings.Join(m.CC, ",")))
}
if len(m.BCC) > 0 {
buf.WriteString(fmt.Sprintf("Bcc: %s\n", strings.Join(m.BCC, ",")))
}
buf.WriteString("MIME-Version: 1.0\n")
writer := multipart.NewWriter(buf)
boundary := writer.Boundary()
if withAttachments {
buf.WriteString(fmt.Sprintf("Content-Type: multipart/mixed; boundary=%s\n", boundary))
buf.WriteString(fmt.Sprintf("--%s\n", boundary))
} else {
buf.WriteString("Content-Type: text/plain; charset=utf-8\n")
}
buf.WriteString(m.Body)
if withAttachments {
for k, v := range m.Attachments {
buf.WriteString(fmt.Sprintf("\n\n--%s\n", boundary))
buf.WriteString(fmt.Sprintf("Content-Type: %s\n", http.DetectContentType(v)))
buf.WriteString("Content-Transfer-Encoding: base64\n")
buf.WriteString(fmt.Sprintf("Content-Disposition: attachment; filename=%s\n", k))
b := make([]byte, base64.StdEncoding.EncodedLen(len(v)))
base64.StdEncoding.Encode(b, v)
buf.Write(b)
buf.WriteString(fmt.Sprintf("\n--%s", boundary))
}
buf.WriteString("--")
}
return buf.Bytes()
}
As you can see, I am using the standard library net/smtp package. Is that Ok to do when you want to send an email through SES? Of course, I am passing my SES SMTP credentials for the necessary/required environment variables.
Right now, I'm not getting any errors, but I am also not receiving emails even though the count on "emails sent" on the SES Dashboard (within the AWS Console) increments each time I send a request to my lambda function.
Am I going about this the wrong way? It is not working because I must use the SES package within the AWS SDK?
In the HTTP handler, I'm doing:
err = r.ParseMultipartForm(10 << 20)
if err != nil {
logger.Error("error parsing form data", zap.Error(err))
http.Error(w, "error parsing form data", http.StatusBadRequest)
return
}
I believe there's a limit of 10Mb on SES emails, and I believe the 10 << 20 ensure I don't go over? Correct me if I'm wrong please.