Twilio SMS

Twilio has the broadest global SMS coverage, a mature deliverability team, and strong APIs for regulated use cases like OTP (Twilio Verify sits on top but this library uses the plain Messaging API).

Pricing

• Trial — free credits to test.
• Per-message — starts at $0.0075/msg in the US, scales up for international. Full matrix: https://www.twilio.com/en-us/sms/pricing.

Setup

1. Create a Twilio account.
2. Buy a phone number or register a short code / alphanumeric sender.
3. Copy Account SID, Auth Token, and the sending number.

import "github.com/gopackx/go-notification/channel/sms/twilio"

notifier.RegisterChannel("sms", twilio.New(twilio.Config{
    AccountSID: os.Getenv("TWILIO_ACCOUNT_SID"),
    AuthToken:  os.Getenv("TWILIO_AUTH_TOKEN"),
    From:       "+14155238886",
}))

Configuration reference

Sending

func (n OTP) Via(u notification.Notifiable) []string {
    return []string{"sms"}
}

func (n OTP) ToSms(u notification.Notifiable) *sms.Message {
    return sms.NewMessage().
        Text("Your code: " + n.Code)
}

func (u User) RouteNotificationFor(channel string) any {
    if channel == "sms" {
        return u.Phone // E.164 — e.g. "+628123456789"
    }
    return nil
}

Troubleshooting

• 21211: invalid 'To' number — not in E.164 format, or a landline that Twilio can't reach.
• 21612: not a valid message sending phone number — your From isn't SMS-enabled, or the destination country requires a specific sender type (short code vs. long code).
• Works in sandbox, fails in prod — trial accounts can only message verified numbers. Upgrade to paid before launching.
• Message never arrives, no error — sometimes carriers silently drop messages flagged as spam. Check Messaging → Logs in the console for a delivered status.