Sending SMS in Go (Golang): API Library Integration

Sending SMS in Go (Golang): API Library Integration

In the modern world, sending SMS messages remains a popular feature for user verification, notifications, and marketing campaigns. In Go (Golang), this is implemented easily and efficiently thanks to built-in tools for working with HTTP and JSON. In this article, we will look at how to write your own library for sending SMS via a REST API using Go. The example will be built on an abstract provider, but the code can be easily adapted to any service (Twilio, SMS.ru, Vonage, etc.).

Library Architecture

Our library will consist of the following components:

• An HTTP request client with support for timeouts and retries
• Structures for the request (number, text, sender) and response (status, message ID, error)
• An initialization function with an API key and base URL
• A SendSMS method for sending a single message

Installation and Preparation

To work, you only need the Go standard library (net/http, encoding/json). No external dependencies are required. Create a file sms.go and import the package:

package smsclient

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

Data Structures

Let's define the types for the request and response:

// SMSRequest represents the request body to the APItype SMSRequest struct {    To      string `json:"to"`      // Recipient number in international format    Text    string `json:"text"`    // Message text    Sender  string `json:"sender"`  // Sender name (alpha-name)}

// SMSResponse contains the sending resulttype SMSResponse struct {    Success   bool   `json:"success"`    MessageID string `json:"message_id,omitempty"`    Error     string `json:"error,omitempty"`}

Client for Working with the API

Let's create a client structure with configuration:

// Client manages sending SMS via the APItype Client struct {    apiKey    string    baseURL   string    httpClient *http.Client}

// NewClient creates a new client instancefunc NewClient(apiKey, baseURL string) *Client {    return &Client{        apiKey:  apiKey,        baseURL: baseURL,        httpClient: &http.Client{            Timeout: 10 * time.Second,        },    }}

SMS Sending Method

Let's implement the main logic — sending a POST request with a JSON body:

// SendSMS sends an SMS and returns the response from the APIfunc (c *Client) SendSMS(req SMSRequest) (*SMSResponse, error) {    // 1. Serialize the request to JSON    body, err := json.Marshal(req)    if err != nil {        return nil, fmt.Errorf("error marshaling request: %w", err)    }

    // 2. Create an HTTP request    httpReq, err := http.NewRequest("POST", c.baseURL+"/sms/send", bytes.NewBuffer(body))    if err != nil {        return nil, fmt.Errorf("error creating request: %w", err)    }

    // 3. Set headers    httpReq.Header.Set("Content-Type", "application/json")    httpReq.Header.Set("Authorization", "Bearer "+c.apiKey)

    // 4. Execute the request    resp, err := c.httpClient.Do(httpReq)    if err != nil {        return nil, fmt.Errorf("error executing request: %w", err)    }    defer resp.Body.Close()

    // 5. Decode the response    var smsResp SMSResponse    if err := json.NewDecoder(resp.Body).Decode(&smsResp); err != nil {        return nil, fmt.Errorf("error decoding response: %w", err)    }

    // 6. Check the HTTP status code    if resp.StatusCode != http.StatusOK {        return &smsResp, fmt.Errorf("API returned code %d: %s", resp.StatusCode, smsResp.Error)    }

    return &smsResp, nil}

Usage Example

Now let's show how to use the library in real code:

package main

impo