Is there experience integrating with external services (banks, payment gateways, APIs)?

Yes, experience with integrating external services in Go typically involves working with REST APIs of banks and payment gateways via HTTP clients, handling JSON/XML, authentication (OAuth, API keys), as well as error and timeout handling.

Example of integration with a payment API:

package main

import (
    "bytes"
    "encoding/json"
    "fmt"
    "net/http"
    "time"
)

type PaymentRequest struct {
    Amount   float64 `json:"amount"`
    Currency string  `json:"currency"`
    CardID   string  `json:"card_id"`
}

type PaymentResponse struct {
    Status  string `json:"status"`
    Message string `json:"message"`
}

func makePayment() error {
    reqBody := PaymentRequest{
        Amount:   100.0,
        Currency: "USD",
        CardID:   "card_123",
    }

    jsonData, err := json.Marshal(reqBody)
    if err != nil {
        return err
    }

    client := &http.Client{Timeout: 10 * time.Second}
    req, err := http.NewRequest("POST", "https://api.paymentgateway.com/pay", bytes.NewBuffer(jsonData))
    if err != nil {
        return err
    }
    req.Header.Set("Content-Type", "application/json")
    req.Header.Set("Authorization", "Bearer your_api_token")

    resp, err := client.Do(req)
    if err != nil {
        return err
    }
    defer resp.Body.Close()

    var paymentResp PaymentResponse
    if err := json.NewDecoder(resp.Body).Decode(&paymentResp); err != nil {
        return err
    }

    fmt.Println("Payment status:", paymentResp.Status)
    return nil
}

func main() {
    if err := makePayment(); err != nil {
        fmt.Println("Error making payment:", err)
    }
}

This approach allows flexible working with external APIs, handling responses and errors, and integrating with various payment systems.