lesson 59: Send Email in Go using Gmail

app.env

@@ -8,4 +8,7 @@ ACCESS_TOKEN_DURATION=15m
 REFRESH_TOKEN_DURATION=24h
 MIGRATION_URL=file://db/migration
 ENVIRONMENT=development
-REDIS_ADDRESS=0.0.0.0:6379
+REDIS_ADDRESS=0.0.0.0:6379
+EMAIL_SENDER_NAME=Blessed Bank
+EMAIL_SENDER_ADDRESS=bmadukoma@gmail.com
+EMAIL_SENDER_PASSWORD=bmadukoma

details.md

@@ -475,3 +475,7 @@
 58. Why delay added to Asynq Tasks is good
     1.  This is good to allow the transaction commit into the db and the sending of email to be done.
 
+59. Send Email in Go using Gmail
+    1.  ran `go get github.com/jordan-wright/email`.
+    2.  created `mail` package and `mail/sender.go` to define mailer interfaces and structs.
+    3.  added mail credentials `app.env`, updated `config.go` to include the email settings in the struct and wrote test for `sender.go` in `sender_test.go`.

go.mod

@@ -36,6 +36,7 @@ require (
 	github.com/golang/protobuf v1.5.3 // indirect
 	github.com/hashicorp/errwrap v1.1.0 // indirect
 	github.com/hashicorp/go-multierror v1.1.1 // indirect
+	github.com/jordan-wright/email v4.0.1-0.20210109023952-943e75fe5223+incompatible // indirect
 	github.com/klauspost/cpuid/v2 v2.2.5 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect
 	github.com/pkg/errors v0.9.1 // indirect

go.sum

@@ -201,6 +201,8 @@ github.com/hibiken/asynq v0.24.1 h1:+5iIEAyA9K/lcSPvx3qoPtsKJeKI5u9aOIvUmSsazEw=
 github.com/hibiken/asynq v0.24.1/go.mod h1:u5qVeSbrnfT+vtG5Mq8ZPzQu/BmCKMHvTGb91uy9Tts=
 github.com/ianlancetaylor/demangle v0.0.0-20181102032728-5e5cf60278f6/go.mod h1:aSSvb/t6k1mPoxDqO4vJh6VOCGPwU4O0C2/Eqndh1Sc=
 github.com/ianlancetaylor/demangle v0.0.0-20200824232613-28f6c0f3b639/go.mod h1:aSSvb/t6k1mPoxDqO4vJh6VOCGPwU4O0C2/Eqndh1Sc=
+github.com/jordan-wright/email v4.0.1-0.20210109023952-943e75fe5223+incompatible h1:jdpOPRN1zP63Td1hDQbZW73xKmzDvZHzVdNYxhnTMDA=
+github.com/jordan-wright/email v4.0.1-0.20210109023952-943e75fe5223+incompatible/go.mod h1:1c7szIrayyPPB/987hsnvNzLushdWf4o/79s3P08L8A=
 github.com/json-iterator/go v1.1.12 h1:PV8peI4a0ysnczrg+LtxykD8LfKY9ML6u2jnxaEnrnM=
 github.com/json-iterator/go v1.1.12/go.mod h1:e30LSqwooZae/UwlEbR2852Gd8hjQvJoHmT4TnhNGBo=
 github.com/jstemmer/go-junit-report v0.0.0-20190106144839-af01ea7f8024/go.mod h1:6v2b51hI/fHJwM22ozAgKL4VKDeJcHhJFhtBdhmNjmU=

mail/sender.go

@@ -0,0 +1,66 @@
+package mail
+
+import (
+	"fmt"
+	"net/smtp"
+
+	"github.com/jordan-wright/email"
+)
+
+const (
+	smtpAuthAddress   = "smtp.gmail.com"
+	smtpServerAddress = "smtp.gmail.com:587"
+)
+
+type EmailSender interface {
+	SendEmail(
+		subject string,
+		content string,
+		to []string,
+		cc []string,
+		bcc []string,
+		attachFiles []string,
+	) error
+}
+
+type GmailSender struct {
+	name              string
+	fromEmailAddress  string
+	fromEmailPassword string
+}
+
+func NewGmailSender(name, fromEmailAddress, fromEmailPassword string) EmailSender {
+	return &GmailSender{
+		name:              name,
+		fromEmailAddress:  fromEmailAddress,
+		fromEmailPassword: fromEmailPassword,
+	}
+}
+
+func (sender *GmailSender) SendEmail(
+	subject string,
+	content string,
+	to []string,
+	cc []string,
+	bcc []string,
+	attachFiles []string,
+) error {
+	e := email.NewEmail()
+	e.From = fmt.Sprintf("%s <%s>", sender.name, sender.fromEmailAddress)
+	e.Subject = subject
+	e.HTML = []byte(content)
+	e.To = to
+	e.Cc = cc
+	e.Bcc = bcc
+
+	for _, file := range attachFiles {
+		_, err := e.AttachFile(file)
+		if err != nil {
+			return fmt.Errorf("failed to attach file - %s: %w", file, err)
+		}
+	}
+
+	smtpAuth := smtp.PlainAuth("", sender.fromEmailAddress, sender.fromEmailPassword, smtpAuthAddress)
+
+	return e.Send(smtpServerAddress, smtpAuth)
+}

mail/sender_test.go

@@ -0,0 +1,28 @@
+package mail
+
+import (
+	"testing"
+
+	"github.com/blessedmadukoma/go-simple-bank/util"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSendEmailWithGmail(t *testing.T) {
+	config, err := util.LoadConfig("../")
+	require.NoError(t, err)
+
+	sender := NewGmailSender(config.EmailSenderName, config.EmailSenderAddress, config.EmailSenderPassword)
+
+	subject := "Hello from Go!"
+	content := `
+	<h1>This is a test email from Go!</h1>
+	<p>Feel free to delete this email.</p>
+	`
+
+	to := []string{"bmadukoma@gmail.com"}
+	files := []string{"../go.mod"}
+
+	err = sender.SendEmail(subject, content, to, nil, nil, files)
+	require.NoError(t, err)
+
+}

util/config.go

@@ -19,6 +19,9 @@ type Config struct {
 	GRPCServerAddress    string        `mapstructure:"GRPC_SERVER_ADDRESS"`
 	AccessTokenDuration  time.Duration `mapstructure:"ACCESS_TOKEN_DURATION"`
 	RefreshTokenDuration time.Duration `mapstructure:"REFRESH_TOKEN_DURATION"`
+	EmailSenderName      string        `mapstructure:"EMAIL_SENDER_NAME"`
+	EmailSenderAddress   string        `mapstructure:"EMAIL_SENDER_ADDRESS"`
+	EmailSenderPassword  string        `mapstructure:"EMAIL_SENDER_PASSWORD"`
 }
 
 // LoadConfig reads configuration from file or env variables