HTTP Advanced Features - Complete Guide with Latest Syntax

package main
import http
import fmt

function downloadFileInChunks(url string, chunkSize int) {
    fmt.Printf("📥 Downloading %s in %d byte chunks\n", url, chunkSize)

    // First, get file size with HEAD request
    var headResponse, headErr = http.Head(url)
    if headErr != None {
        fmt.Printf("❌ Failed to get file info: %s\n", headErr)
        return
    }

    var contentLength = headResponse["headers"]["Content-Length"]
    fmt.Printf("📊 File size: %s bytes\n", contentLength)

    var downloaded = 0
    var totalSize = 10000  // Simulated file size

    for downloaded < totalSize {
        var start = downloaded
        var end = downloaded + chunkSize - 1
        if end >= totalSize {
            end = totalSize - 1
        }

        // Create request with Range header
        var request, _ = http.NewRequest("GET", url, "")
        var rangeHeader = "bytes=" + start + "-" + end
        var rangeRequest, _ = http.SetHeader(request, "Range", rangeHeader)

        var response, err = http.Do(rangeRequest)
        if err != None {
            fmt.Printf("❌ Chunk download failed: %s\n", err)
            return
        }

        if response["status"] == 206 {  // Partial Content
            fmt.Printf("✅ Downloaded bytes %d-%d (%d bytes)\n", start, end, end-start+1)
            downloaded = end + 1
        } else {
            fmt.Printf("❌ Server doesn't support range requests (Status: %d)\n", response["status"])
            return
        }
    }

    fmt.Printf("🎉 Download complete!\n")
}

package main
import http
import fmt

function resumeDownload(url string, existingBytes int) {
    var request, _ = http.NewRequest("GET", url, "")
    var rangeHeader = "bytes=" + existingBytes + "-"
    var resumeRequest, _ = http.SetHeader(request, "Range", rangeHeader)

    var response, err = http.Do(resumeRequest)
    if err != None {
        fmt.Printf("❌ Resume failed: %s\n", err)
        return
    }

    if response["status"] == 206 {
        fmt.Printf("✅ Resuming download from byte %d\n", existingBytes)
    } else {
        fmt.Printf("⚠️  Server doesn't support resume, starting over\n")
    }
}

package main
import http
import fmt

// Fetch with ETag validation
function fetchWithETag(url string, cachedETag string) {
    var request, _ = http.NewRequest("GET", url, "")

    if cachedETag != "" {
        var conditionalRequest, _ = http.SetHeader(request, "If-None-Match", cachedETag)
        var response, err = http.Do(conditionalRequest)

        if err != None {
            fmt.Printf("❌ Request failed: %s\n", err)
            return
        }

        if response["status"] == 304 {
            fmt.Printf("✅ Content not modified - using cache\n")
            return  // Use cached content
        }
    }

    // Fetch new content
    var response, err = http.Get(url)
    if err != None {
        fmt.Printf("❌ Request failed: %s\n", err)
        return
    }

    var newETag = response["headers"]["ETag"]
    fmt.Printf("✅ New content received - ETag: %s\n", newETag)
}

package main
import http
import fmt

function fetchIfModified(url string, lastModified string) {
    var request, _ = http.NewRequest("GET", url, "")

    if lastModified != "" {
        request, _ = http.SetHeader(request, "If-Modified-Since", lastModified)
    }

    var response, err = http.Do(request)
    if err != None {
        fmt.Printf("❌ Request failed: %s\n", err)
        return
    }

    if response["status"] == 304 {
        fmt.Printf("✅ Content not modified since %s\n", lastModified)
    } else {
        var newLastModified = response["headers"]["Last-Modified"]
        fmt.Printf("✅ Content updated - Last-Modified: %s\n", newLastModified)
    }
}

package main
import http
import fmt

function requestWithTimeout(url string, timeoutSeconds int) {
    fmt.Printf("⏱️  Making request with %d second timeout\n", timeoutSeconds)

    var request, _ = http.NewRequest("GET", url, "")
    // Note: In full implementation, timeout would be set on request

    var response, err = http.Do(request)

    if err != None {
        if err == "request timeout" or err == "context deadline exceeded" {
            fmt.Printf("⏰ Request timed out after %d seconds\n", timeoutSeconds)
        } else {
            fmt.Printf("❌ Request failed: %s\n", err)
        }
        return
    }

    fmt.Printf("✅ Request completed within timeout - Status: %d\n", response["status"])
}

package main
import http
import fmt

function cancellableRequestChain(urls array, timeoutPerRequest int) {
    fmt.Printf("🔗 Processing %d URLs with %ds timeout each\n", len(urls), timeoutPerRequest)

    for i, url in urls {
        fmt.Printf("🔄 Request %d/%d: %s\n", i+1, len(urls), url)

        var response, err = http.Get(url)

        if err != None {
            fmt.Printf("❌ Request %d failed: %s\n", i+1, err)
            continue  // Continue with next URL
        }

        fmt.Printf("✅ Request %d completed - Status: %d\n", i+1, response["status"])
    }
}

package main
import http
import fmt

// Logging middleware
function loggingMiddleware(next function) {
    return function(request, response) {
        var method = request["method"]
        var path = request["url"]
        fmt.Printf("🔄 [LOG] %s %s - Started\n", method, path)

        next(request, response)

        var status = response["status"]
        fmt.Printf("✅ [LOG] %s %s - Completed (%d)\n", method, path, status)
    }
}

// Authentication middleware
function authMiddleware(next function) {
    return function(request, response) {
        var authHeader = request["headers"]["Authorization"]

        if authHeader == None or authHeader == "" {
            fmt.Printf("❌ [AUTH] No authorization header\n")
            response["status"] = 401
            return
        }

        if authHeader == "Bearer valid-token" {
            fmt.Printf("✅ [AUTH] Valid token\n")
            next(request, response)
        } else {
            fmt.Printf("❌ [AUTH] Invalid token\n")
            response["status"] = 403
        }
    }
}

// CORS middleware
function corsMiddleware(next function) {
    return function(request, response) {
        fmt.Printf("🌐 [CORS] Adding CORS headers\n")

        if request["method"] == "OPTIONS" {
            fmt.Printf("✅ [CORS] Preflight handled\n")
            response["status"] = 200
            return
        }

        next(request, response)
    }
}

### Middleware Chain Composition

```harneet title="Middleware Chain Composition"
package main
import http
import fmt

// Compose middleware chain
function createMiddlewareChain(middlewares array, handler function) {
    var result = handler

    // Apply middlewares in reverse order
    for middleware in middlewares {
        result = middleware(result)
    }

    return result
}

// Example handler
function apiHandler(request, response) {
    fmt.Printf("📄 [HANDLER] Processing API request\n")
    response["status"] = 200
}

// Usage
var middlewares = [loggingMiddleware, corsMiddleware, authMiddleware]
var protectedHandler = createMiddlewareChain(middlewares, apiHandler)

## Request Cloning

Methods to clone and modify HTTP requests for middleware and testing.

### Request Variation Testing

```harneet title="Request Variation Testing"
package main
import http
import fmt

function testRequestVariations(baseURL string, endpoint string) {
    // Test different authentication methods
    var testCases = [
        {"name": "No Auth", "header": "", "value": ""},
        {"name": "Bearer Token", "header": "Authorization", "value": "Bearer token123"},
        {"name": "API Key", "header": "X-API-Key", "value": "api-key-456"},
        {"name": "Basic Auth", "header": "Authorization", "value": "Basic dXNlcjpwYXNz"}
    ]

    for testCase in testCases {
        fmt.Printf("\n🧪 Testing: %s\n", testCase["name"])

        // Clone base request
        var testRequest, _ = http.NewRequest("GET", baseURL + endpoint, "")
        testRequest, _ = http.SetHeader(testRequest, "User-Agent", "TestClient/1.0")

        // Add test-specific header
        if testCase["header"] != "" {
            testRequest, _ = http.SetHeader(testRequest, testCase["header"], testCase["value"])
        }

        var response, err = http.Do(testRequest)

        if err != None {
            fmt.Printf("❌ Test failed: %s\n", err)
        } else {
            fmt.Printf("✅ Status: %d\n", response["status"])
        }
    }
}

### Retry with Request Modifications

```harneet title="Retry with Request Modifications"
package main
import http
import fmt
import time

function retryWithModifications(originalURL string, maxRetries int) {
    for attempt in range(maxRetries) {
        var request, _ = http.NewRequest("GET", originalURL, "")

        // Add retry-specific headers
        request, _ = http.SetHeader(request, "X-Retry-Attempt", attempt + 1)
        request, _ = http.SetHeader(request, "X-Request-ID", "req-" + (attempt + 1))

        var response, err = http.Do(request)

        if err == None and response["status"] < 500 {
            fmt.Printf("✅ Success on attempt %d\n", attempt + 1)
            return
        }

        fmt.Printf("⏳ Attempt %d failed, retrying...\n", attempt + 1)
    }
}

## Multipart Forms

Built-in support for parsing multipart/form-data including file uploads.

### Multipart Form Upload

```harneet title="Multipart Form Upload"
package main
import http
import fmt

function uploadMultipartForm(url string, fields map, files array) {
    var boundary = "----WebKitFormBoundary7MA4YWxkTrZu0gW"
    var multipartBody = ""

    // Add form fields
    for key, value in fields {
        multipartBody = multipartBody + "--" + boundary + "\r\n"
        multipartBody = multipartBody + "Content-Disposition: form-data; name=\"" + key + "\"\r\n\r\n"
        multipartBody = multipartBody + value + "\r\n"
    }

    // Add files
    for file in files {
        multipartBody = multipartBody + "--" + boundary + "\r\n"
        multipartBody = multipartBody + "Content-Disposition: form-data; name=\"" + file["field"] + "\"; filename=\"" + file["name"] + "\"\r\n"
        multipartBody = multipartBody + "Content-Type: " + file["type"] + "\r\n\r\n"
        multipartBody = multipartBody + file["content"] + "\r\n"
    }

    multipartBody = multipartBody + "--" + boundary + "--\r\n"

    var response, err = http.Post(url, "multipart/form-data; boundary=" + boundary, multipartBody)

    if err != None {
        fmt.Printf("❌ Upload failed: %s\n", err)
    } else if response["status"] == 200 {
        fmt.Printf("✅ Upload successful!\n")
    } else {
        fmt.Printf("❌ Upload failed - Status: %d\n", response["status"])
    }
}

### File Upload with Validation

```harneet title="File Upload with Validation"
package main
import http
import fmt

function uploadWithValidation(url string, filename string, content string, maxSize int) {
    if len(content) > maxSize {
        fmt.Printf("❌ File too large: %d bytes (max: %d)\n", len(content), maxSize)
        return
    }

    var allowedTypes = ["txt", "pdf", "jpg", "png"]
    var extension = getFileExtension(filename)
    var isAllowed = false

    for allowedType in allowedTypes {
        if extension == allowedType {
            isAllowed = true
            break
        }
    }

    if !isAllowed {
        fmt.Printf("❌ File type not allowed: %s\n", extension)
        return
    }

    var fields = {"description": "File upload", "category": "document"}
    var files = [{"field": "file", "name": filename, "type": "text/plain", "content": content}]

    uploadMultipartForm(url, fields, files)
}

function getFileExtension(filename string) string {
    // Simplified extension extraction
    return "txt"  // In real implementation, extract from filename
}

## Keep-Alive Control

Connection keep-alive management and configuration options.

### Optimized Client with Keep-Alive

```harneet title="Optimized Client with Keep-Alive"
package main
import http
import fmt

function createOptimizedClient(maxConnections int, keepAliveTimeout int) map {
    return {
        "maxConnections": maxConnections,
        "keepAliveTimeout": keepAliveTimeout,
        "userAgent": "OptimizedClient/1.0"
    }
}

function makeOptimizedRequest(client map, url string) {
    var request, _ = http.NewRequest("GET", url, "")

    // Set keep-alive headers
    request, _ = http.SetHeader(request, "Connection", "keep-alive")
    request, _ = http.SetHeader(request, "Keep-Alive", "timeout=" + client["keepAliveTimeout"])
    request, _ = http.SetHeader(request, "User-Agent", client["userAgent"])

    var response, err = http.Do(request)

    if err != None {
        fmt.Printf("❌ Request failed: %s\n", err)
        return
    }

    var connection = response["headers"]["Connection"]
    if connection == "keep-alive" {
        fmt.Printf("✅ Keep-alive connection established\n")
    }

    fmt.Printf("✅ Request completed - Status: %d\n", response["status"])
}

### Batch Requests with Connection Reuse

```harneet title="Batch Requests with Connection Reuse"
package main
import http
import fmt

function batchRequestsWithKeepAlive(client map, urls array) {
    fmt.Printf("📦 Processing %d URLs with connection reuse\n", len(urls))

    for i, url in urls {
        fmt.Printf("🔄 Request %d/%d: %s\n", i+1, len(urls), url)
        makeOptimizedRequest(client, url)
    }

    fmt.Printf("🎉 Batch complete with optimized connections\n")
}

// Usage
var client = createOptimizedClient(10, 30)  // 10 connections, 30s timeout
var urls = [
    "https://api.example.com/users",
    "https://api.example.com/posts", 
    "https://api.example.com/comments"
]
batchRequestsWithKeepAlive(client, urls)

package main
import http
import json
import fmt

function createAdvancedHTTPClient() map {
    return {
        "timeout": 30,
        "retries": 3,
        "keepAlive": true,
        "userAgent": "AdvancedClient/1.0"
    }
}

function advancedRequest(client map, method string, url string, body string, options map) {
    var request, _ = http.NewRequest(method, url, body)

    // Apply client defaults
    request, _ = http.SetHeader(request, "User-Agent", client["userAgent"])

    // Apply conditional headers if provided
    if options["etag"] != None {
        request, _ = http.SetHeader(request, "If-None-Match", options["etag"])
    }

    if options["lastModified"] != None {
        request, _ = http.SetHeader(request, "If-Modified-Since", options["lastModified"])
    }

    // Apply range if provided
    if options["rangeStart"] != None and options["rangeEnd"] != None {
        var rangeHeader = "bytes=" + options["rangeStart"] + "-" + options["rangeEnd"]
        request, _ = http.SetHeader(request, "Range", rangeHeader)
    }

    // Retry with exponential backoff
    var attempt = 0
    for attempt < client["retries"] {
        attempt = attempt + 1

        var requestCopy, _ = http.NewRequest(method, url, body)
        requestCopy, _ = http.SetHeader(requestCopy, "X-Attempt", attempt)

        var response, err = http.Do(requestCopy)

        if err == None {
            return response, None
        }

        if attempt < client["retries"] {
            var backoff = attempt * 2
            fmt.Printf("⏳ Attempt %d failed, retrying in %d seconds...\n", attempt, backoff)
        }
    }

    return None, "All retry attempts failed"
}

// Usage
var client = createAdvancedHTTPClient()
var options = {"etag": "\"abc123\"", "rangeStart": 0, "rangeEnd": 1023}
var response, err = advancedRequest(client, "GET", "https://api.example.com/data", "", options)

if existingSize > 0 {
    fmt.Printf("🔄 Resuming download from byte %d\n", existingSize)

    var request, _ = http.NewRequest("GET", url, "")
    var rangeRequest, _ = http.SetRange(request, existingSize, -1)  // -1 means to end
    var response, err = http.Do(rangeRequest)

    if err != None {
        fmt.Printf("❌ Resume failed: %s\n", err)
        return
    }

    if response["status"] == 206 {
        fmt.Printf("✅ Resuming download...\n")
        // Append to existing file: response["body"]
    } else {
        fmt.Printf("⚠️  Server doesn't support resume, starting over\n")
        // Start fresh download
    }
}

import http
import fmt

function fetchIfModified(url string, lastModified string) {
    var request, _ = http.NewRequest("GET", url, "")

    if lastModified != "" {
        var conditionalRequest, _ = http.SetHeader(request, "If-Modified-Since", lastModified)
        var response, err = http.Do(conditionalRequest)

        if err != None {
            fmt.Printf("❌ Request failed: %s\n", err)
            return None
        }

        if response["status"] == 304 {
            fmt.Printf("✅ Content not modified since %s\n", lastModified)
            return None  // Use cached content
        }
    }

    var response, err = http.Do(request)
    if err != None {
        return None
    }

    var newLastModified = response["headers"]["Last-Modified"]
    fmt.Printf("✅ Content modified, new date: %s\n", newLastModified)
    return response["body"]
}

import http
import fmt

function fetchWithTimeout(url string, timeoutSeconds int) {
    var request, _ = http.NewRequest("GET", url, "")
    var timeoutRequest, _ = http.WithTimeout(request, timeoutSeconds)

    var response, err = http.Do(timeoutRequest)

    if err != None {
        if err == "request timeout" {
            fmt.Printf("⏰ Request timed out after %d seconds\n", timeoutSeconds)
        } else {
            fmt.Printf("❌ Request failed: %s\n", err)
        }
        return None
    }

    fmt.Printf("✅ Request completed within timeout\n")
    return response
}

// Usage
var response = fetchWithTimeout("https://slow-api.example.com/data", 5)

import http
import fmt

function fetchMultipleWithCancel(urls array, timeoutSeconds int) {
    var results = []

    for url in urls {
        fmt.Printf("🔄 Fetching: %s\n", url)

        var request, _ = http.NewRequest("GET", url, "")
        var timeoutRequest, _ = http.WithTimeout(request, timeoutSeconds)
        var response, err = http.Do(timeoutRequest)

        if err != None {
            fmt.Printf("❌ Failed to fetch %s: %s\n", url, err)
            // Continue with next URL or break based on strategy
            continue
        }

        results = append(results, {
            "url": url,
            "status": response["status"],
            "data": response["body"]
        })

        fmt.Printf("✅ Completed: %s (Status: %d)\n", url, response["status"])
    }

    return results
}

import http
import fmt
import time

function loggingMiddleware(next function) {
    return function(request, response) {
        var start = time.Now()
        var method = request["method"]
        var path = request["path"]

        fmt.Printf("🔄 %s %s - Started\n", method, path)

        // Call next handler
        next(request, response)

        var duration = time.Since(start)
        var status = response["status"]
        fmt.Printf("✅ %s %s - %d (%s)\n", method, path, status, duration)
    }
}

function authMiddleware(next function) {
    return function(request, response) {
        var authHeader = request["headers"]["Authorization"]

        if authHeader == None or authHeader == "" {
            http.WriteResponse(response, 401, "application/json", 
                "{\"error\": \"Authorization required\"}")
            return
        }

        // Validate token (simplified)
        if !isValidToken(authHeader) {
            http.WriteResponse(response, 403, "application/json", 
                "{\"error\": \"Invalid token\"}")
            return
        }

        // Add user info to request context
        request["user"] = getUserFromToken(authHeader)
        next(request, response)
    }
}

function corsMiddleware(next function) {
    return function(request, response) {
        // Set CORS headers
        response["headers"]["Access-Control-Allow-Origin"] = "*"
        response["headers"]["Access-Control-Allow-Methods"] = "GET, POST, PUT, DELETE, OPTIONS"
        response["headers"]["Access-Control-Allow-Headers"] = "Content-Type, Authorization"

        if request["method"] == "OPTIONS" {
            http.WriteResponse(response, 200, "text/plain", "")
            return
        }

        next(request, response)
    }
}

// Chain middleware
function createProtectedHandler(handler function) {
    return corsMiddleware(
        loggingMiddleware(
            authMiddleware(handler)
        )
    )
}

// Usage
function apiHandler(request, response) {
    var user = request["user"]
    var data = {"message": "Hello " + user["name"], "protected": true}
    var jsonData, _ = json.Marshal(data)
    http.WriteResponse(response, 200, "application/json", jsonData)
}

var protectedHandler = createProtectedHandler(apiHandler)
http.HandleFunc(mux, "/api/protected", protectedHandler)

import http
import fmt
import time

// Simple in-memory rate limiter
var rateLimiter = {}

function rateLimitMiddleware(requestsPerMinute int) {
    return function(next function) {
        return function(request, response) {
            var clientIP = request["remote_addr"]
            var now = time.Now()
            var minute = now / 60  // Simple minute bucket
            var key = clientIP + ":" + minute

            var count = rateLimiter[key]
            if count == None {
                count = 0
            }

            if count >= requestsPerMinute {
                http.WriteResponse(response, 429, "application/json", 
                    "{\"error\": \"Rate limit exceeded\"}")
                return
            }

            rateLimiter[key] = count + 1
            next(request, response)
        }
    }
}

// Usage
var rateLimitedHandler = rateLimitMiddleware(100)(apiHandler)

import http
import fmt

function testAPIWithDifferentHeaders(baseRequest map) {
    var testCases = [
        {"User-Agent": "TestBot/1.0", "expected": 200},
        {"User-Agent": "BadBot/1.0", "expected": 403},
        {"Authorization": "Bearer valid-token", "expected": 200},
        {"Authorization": "Bearer invalid-token", "expected": 401}
    ]

    for testCase in testCases {
        // Clone the base request
        var testRequest, _ = http.CloneRequest(baseRequest)

        // Modify headers for this test
        for header, value in testCase {
            if header != "expected" {
                testRequest, _ = http.SetHeader(testRequest, header, value)
            }
        }

        var response, err = http.Do(testRequest)
        var expectedStatus = testCase["expected"]

        if err != None {
            fmt.Printf("❌ Test failed: %s\n", err)
            continue
        }

        if response["status"] == expectedStatus {
            fmt.Printf("✅ Test passed: %s = %d\n", testCase, expectedStatus)
        } else {
            fmt.Printf("❌ Test failed: expected %d, got %d\n", expectedStatus, response["status"])
        }
    }
}

// Usage
var baseRequest, _ = http.NewRequest("GET", "https://api.example.com/test", "")
testAPIWithDifferentHeaders(baseRequest)

import http
import fmt
import time

function retryWithBackoff(originalRequest map, maxRetries int) {
    var attempt = 0

    for attempt < maxRetries {
        attempt = attempt + 1

        // Clone request for this attempt
        var request, _ = http.CloneRequest(originalRequest)

        // Add retry headers
        request, _ = http.SetHeader(request, "X-Retry-Attempt", attempt)
        request, _ = http.SetHeader(request, "X-Request-ID", generateRequestID())

        var response, err = http.Do(request)

        if err == None and response["status"] < 500 {
            fmt.Printf("✅ Request succeeded on attempt %d\n", attempt)
            return response
        }

        if attempt < maxRetries {
            var backoffSeconds = attempt * 2  // Exponential backoff
            fmt.Printf("⏳ Attempt %d failed, retrying in %d seconds...\n", attempt, backoffSeconds)
            time.Sleep(backoffSeconds)
        }
    }

    fmt.Printf("❌ All %d attempts failed\n", maxRetries)
    return None
}

import http
import fmt
import os

function fileUploadHandler(request, response) {
    if request["method"] != "POST" {
        http.WriteResponse(response, 405, "text/plain", "Method not allowed")
        return
    }

    var contentType = request["headers"]["Content-Type"]
    if !strings.Contains(contentType, "multipart/form-data") {
        http.WriteResponse(response, 400, "application/json", 
            "{\"error\": \"Expected multipart/form-data\"}")
        return
    }

    var multipart, err = http.ParseMultipart(request)
    if err != None {
        http.WriteResponse(response, 400, "application/json", 
            "{\"error\": \"Failed to parse multipart data\"}")
        return
    }

    // Process form fields
    var description = multipart["fields"]["description"]
    var category = multipart["fields"]["category"]

    // Process uploaded files
    var uploadedFiles = []
    for file in multipart["files"] {
        var filename = file["filename"]
        var content = file["content"]
        var size = file["size"]

        // Save file
        var savedPath, saveErr = os.WriteFile("uploads/" + filename, content)
        if saveErr != None {
            fmt.Printf("❌ Failed to save %s: %s\n", filename, saveErr)
            continue
        }

        uploadedFiles = append(uploadedFiles, {
            "filename": filename,
            "size": size,
            "path": savedPath
        })

        fmt.Printf("✅ Saved file: %s (%d bytes)\n", filename, size)
    }

    var result = {
        "message": "Upload successful",
        "description": description,
        "category": category,
        "files": uploadedFiles
    }

    var jsonResponse, _ = json.Marshal(result)
    http.WriteResponse(response, 200, "application/json", jsonResponse)
}

// Register handler
http.HandleFunc(mux, "/upload", fileUploadHandler)

import http
import fmt

function processFormData(request, response) {
    var multipart, err = http.ParseMultipart(request)
    if err != None {
        http.WriteResponse(response, 400, "application/json", 
            "{\"error\": \"Invalid form data\"}")
        return
    }

    // Validate required fields
    var requiredFields = ["name", "email", "message"]
    var missingFields = []

    for field in requiredFields {
        if multipart["fields"][field] == None or multipart["fields"][field] == "" {
            missingFields = append(missingFields, field)
        }
    }

    if len(missingFields) > 0 {
        var errorMsg = "Missing required fields: " + strings.Join(missingFields, ", ")
        http.WriteResponse(response, 400, "application/json", 
            "{\"error\": \"" + errorMsg + "\"}")
        return
    }

    // Process the form
    var formData = {
        "name": multipart["fields"]["name"],
        "email": multipart["fields"]["email"],
        "message": multipart["fields"]["message"],
        "timestamp": time.Now()
    }

    // Save to database or process as needed
    fmt.Printf("📝 Form submitted by: %s (%s)\n", formData["name"], formData["email"])

    var response = {"message": "Form submitted successfully", "id": generateID()}
    var jsonResponse, _ = json.Marshal(response)
    http.WriteResponse(response, 200, "application/json", jsonResponse)
}

import http
import fmt

function createOptimizedClient(maxConnections int, keepAliveTimeout int) {
    var client = {
        "maxConnections": maxConnections,
        "keepAliveTimeout": keepAliveTimeout,
        "connections": {}
    }

    return client
}

function makeOptimizedRequest(client map, url string) {
    var request, _ = http.NewRequest("GET", url, "")

    // Enable keep-alive with timeout
    var keepAliveRequest, _ = http.SetKeepAlive(request, true, client["keepAliveTimeout"])

    // Set connection pooling headers
    keepAliveRequest, _ = http.SetHeader(keepAliveRequest, "Connection", "keep-alive")
    keepAliveRequest, _ = http.SetHeader(keepAliveRequest, "Keep-Alive", "timeout=" + client["keepAliveTimeout"])

    var response, err = http.Do(keepAliveRequest)

    if err != None {
        fmt.Printf("❌ Request failed: %s\n", err)
        return None
    }

    fmt.Printf("✅ Request completed with keep-alive\n")
    return response
}

// Usage
var client = createOptimizedClient(10, 30)  // 10 connections, 30s timeout

// Make multiple requests that reuse connections
var urls = ["https://api.example.com/users", "https://api.example.com/posts", "https://api.example.com/comments"]
for url in urls {
    var response = makeOptimizedRequest(client, url)
    // Process response
}

import http
import fmt

function createKeepAliveServer(addr string, keepAliveTimeout int) {
    var server, _ = http.NewServer(addr)

    // Configure keep-alive settings
    server["keepAliveTimeout"] = keepAliveTimeout
    server["maxKeepAliveRequests"] = 100
    server["keepAliveEnabled"] = true

    return server
}

function keepAliveHandler(request, response) {
    // Set keep-alive response headers
    response["headers"]["Connection"] = "keep-alive"
    response["headers"]["Keep-Alive"] = "timeout=30, max=100"

    var data = {"message": "Keep-alive enabled", "timestamp": time.Now()}
    var jsonData, _ = json.Marshal(data)
    http.WriteResponse(response, 200, "application/json", jsonData)
}

// Usage
var server = createKeepAliveServer(":8080", 30)
var mux, _ = http.NewMux()
http.HandleFunc(mux, "/api/data", keepAliveHandler)
http.SetHandler(server, mux)

fmt.Println("🚀 Keep-alive server starting on :8080")
http.ListenAndServe(server)

import http
import json
import fmt
import time

function createAdvancedHTTPClient() {
    return {
        "timeout": 30,
        "retries": 3,
        "keepAlive": true,
        "userAgent": "AdvancedClient/1.0"
    }
}

function advancedRequest(client map, method string, url string, body string, options map) {
    var request, _ = http.NewRequest(method, url, body)

    // Apply client defaults
    request, _ = http.WithTimeout(request, client["timeout"])
    request, _ = http.SetKeepAlive(request, client["keepAlive"], 30)
    request, _ = http.SetHeader(request, "User-Agent", client["userAgent"])

    // Apply conditional headers if provided
    if options["etag"] != None {
        request, _ = http.SetHeader(request, "If-None-Match", options["etag"])
    }

    if options["lastModified"] != None {
        request, _ = http.SetHeader(request, "If-Modified-Since", options["lastModified"])
    }

    // Apply range if provided
    if options["rangeStart"] != None and options["rangeEnd"] != None {
        request, _ = http.SetRange(request, options["rangeStart"], options["rangeEnd"])
    }

    // Retry with exponential backoff
    var attempt = 0
    for attempt < client["retries"] {
        attempt = attempt + 1

        var requestCopy, _ = http.CloneRequest(request)
        requestCopy, _ = http.SetHeader(requestCopy, "X-Attempt", attempt)

        var response, err = http.Do(requestCopy)

        if err == None {
            return response, None
        }

        if attempt < client["retries"] {
            var backoff = attempt * 2
            fmt.Printf("⏳ Attempt %d failed, retrying in %d seconds...\n", attempt, backoff)
            time.Sleep(backoff)
        }
    }

    return None, "All retry attempts failed"
}

// Usage
var client = createAdvancedHTTPClient()
var options = {"etag": "\"abc123\"", "rangeStart": 0, "rangeEnd": 1023}
var response, err = advancedRequest(client, "GET", "https://api.example.com/data", "", options)