Examples
Email via API (Mailgun / SendGrid)
A complete minimal program that sends email via an API-based driver.
This is the recommended production setup — API-based driver instead of SMTP, so it works on any cloud host (see SMTP Port Blocking).
Mailgun variant
package main
import (
"context"
"log"
"os"
"time"
notification "github.com/gopackx/go-notification"
"github.com/gopackx/go-notification/channel/mail"
"github.com/gopackx/go-notification/channel/mail/mailgun"
)
type User struct {
ID string
Name string
Email string
}
func (u User) GetID() string { return u.ID }
func (u User) RouteNotificationFor(channel string) string {
if channel == "mail" {
return u.Email
}
return ""
}
type PasswordReset struct {
ResetURL string
}
func (n PasswordReset) Via(_ notification.Notifiable) []string { return []string{"mail"} }
func (n PasswordReset) ToMail(notifiable notification.Notifiable) *mail.Message {
u := notifiable.(User)
return mail.NewMessage().
SetSubject("Reset your password").
SetGreeting("Hi " + u.Name + ",").
Line("We received a request to reset your password.").
Action("Reset password", n.ResetURL).
Line("This link expires in 30 minutes. If you didn't request this, ignore this email.")
}
func main() {
notifier := notification.New(notification.Config{})
notifier.RegisterChannel(mailgun.New(mailgun.Config{
Domain: "mg.example.com",
APIKey: os.Getenv("MAILGUN_API_KEY"),
From: mail.Address{Name: "Acme", Address: "no-reply@example.com"},
}))
ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
defer cancel()
user := User{ID: "1", Name: "Dani", Email: "dani@example.com"}
if err := notifier.Send(ctx, user, PasswordReset{
ResetURL: "https://app.example.com/reset?token=abc",
}); err != nil {
log.Fatal(err)
}
notifier.Close()
}SendGrid variant
Swap the channel registration only — notification code is identical.
import (
"github.com/gopackx/go-notification/channel/mail"
"github.com/gopackx/go-notification/channel/mail/sendgrid"
)
notifier.RegisterChannel(sendgrid.New(sendgrid.Config{
APIKey: os.Getenv("SENDGRID_API_KEY"),
From: mail.Address{Name: "Acme", Address: "no-reply@example.com"},
}))Env setup
# Mailgun
export MAILGUN_API_KEY=key-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
# or SendGrid
export SENDGRID_API_KEY=SG.xxxxxxxxxxxxxxxxxxxxxx.xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
go run .Deliverability checklist
If your mail lands in spam:
- Verify SPF, DKIM, and DMARC on your sending domain. Both Mailgun and SendGrid walk you through this in their dashboards — don't skip any record.
- Use a dedicated subdomain for transactional mail (e.g.
mg.example.comormail.example.com). Reputation on that subdomain is independent of your main domain's web traffic. - Warm up a new sending domain — start with low volume for the first 2–4 weeks and ramp gradually.
- Handle bounces and complaints. When the provider reports a hard bounce, mark that address as undeliverable in your DB and stop sending to it.
- Avoid marketing-looking subject lines for transactional mail — words like "FREE", "GUARANTEED", all-caps, or lots of emojis can trip spam filters.
Testing locally without sending
Replace the driver with Mailtrap in sandbox mode:
import (
"strconv"
"github.com/gopackx/go-notification/channel/mail"
"github.com/gopackx/go-notification/channel/mail/mailtrap"
)
if os.Getenv("APP_ENV") == "production" {
notifier.RegisterChannel(mailgun.New(mailgun.Config{ /* ... */ }))
} else {
inboxID, _ := strconv.Atoi(os.Getenv("MAILTRAP_INBOX_ID"))
notifier.RegisterChannel(mailtrap.New(mailtrap.Config{
Sandbox: true,
APIToken: os.Getenv("MAILTRAP_API_TOKEN"),
InboxID: inboxID,
From: mail.Address{Name: "Dev", Address: "dev@example.com"},
}))
}Mail in dev goes to a Mailtrap inbox; in prod, to real inboxes. No code change between environments.