MSG91

MSG91 is the standard SMS gateway for India. Unlike the other providers, it is template-driven — it sends DLT-approved Flow templates, not free text.

go get github.com/KARTIKrocks/gosms/msg91

Configuration

provider, err := msg91.NewProvider(msg91.Config{
    AuthKey:    "your_authkey",
    SenderID:   "SENDER",         // 6-char DLT sender ID
    TemplateID: "tmpl_xxx",       // DLT-approved Flow template
    Route:      msg91.RouteTransactional,
})
if err != nil {
    log.Fatal(err)
}

client := gosms.NewClient(provider)

msg := gosms.NewMessage("+919876543210", "")
msg91.SetVar(msg, "name", "Kartik")
msg91.SetVar(msg, "otp", "1234")

result, err := client.SendMessage(ctx, msg)

Field	Purpose
AuthKey	MSG91 API auth key
SenderID	6-character DLT-registered sender ID
TemplateID	Default DLT-approved Flow template
Route	msg91.RouteTransactional (default, route 4) or msg91.RoutePromotional (route 1)
Country	Default country code used to normalize short numbers — see below (default 91)
ShortURL	Enable MSG91's URL shortening
MaxRecipientsPerCall	Chunk size for SendBulk (default 1000; negative disables chunking)
HTTPClient	Optional — override the default *http.Client
BaseURL	Optional — override the MSG91 API base URL (testing)

Template variables and Body fallback

MSG91 Flow templates reference placeholders like ##name## or ##otp##. Set each one with msg91.SetVar. For templates with a single ##body## placeholder, any non-empty Message.Body is automatically passed as body when no vars are set — so the unified client.Send(ctx, to, text) path works without extra wiring.

Per-message overrides

msg91.SetTemplateID(msg, "tmpl_other")  // override Config.TemplateID
msg.WithFrom("OTHER")                   // override the sender ID

Phone normalization

Non-E.164 numbers up to 10 digits are prefixed with Config.Country (default 91). +919876543210, 919876543210, and 9876543210 all normalize identically.

Bulk chunking

SendBulk groups recipients by effective (template_id, sender) and sends each group as one Flow API call. Groups larger than Config.MaxRecipientsPerCall (default 1000) are automatically chunked across multiple calls; set a negative value to disable chunking.

OTP

MSG91 implements the optional gosms.OTPProvider capability for the full send / verify / resend flow, including server-side code generation. See OTP for the full example.

Webhook

Delivery status is webhook-driven; parse incoming callbacks with msg91.ParseWebhook(r) — see Webhooks for the shared pattern.