Every Nepali payment gateway. One Go interface.

var p paynp.Provider = khalti.New(cfg)

// 1. Start: redirect or auto-submit form
co, _ := p.Initiate(ctx, paynp.InitiateRequest{
    TxnID:      "ord-42",
    Amount:     150000, // Rs 1,500 in paisa
    SuccessURL: "https://shop.np/return",
})
co.Write(w, r)

// 2. Return: trust only Lookup
tx, err := p.Lookup(ctx, paynp.LookupRequest{
    TxnID: "ord-42", Amount: 150000,
    ProviderRef: co.ProviderRef,
})
if err == nil && tx.Status == paynp.StatusSuccess {
    fulfil(order)
}