index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Go Calculator</title>
    <link rel="stylesheet" href="style.css">
</head>
<body>
    <div class="container">
        <h1>Go Web Calculator</h1>
        <form method="POST" action="/">
            <input type="text" name="num1" placeholder="Enter first number" required>
            <select name="operator">
                <option value="+">+</option>
                <option value="-">-</option>
                <option value="*">*</option>
                <option value="/">/</option>
            </select>
            <input type="text" name="num2" placeholder="Enter second number" required>
            <button type="submit">Calculate</button>
        </form>
        <div class="result">
            {{if .}}
                <p>{{.}}</p>
            {{end}}
        </div>
    </div>
</body>
</html>