<form action="<your api gateway url>" method="POST" id="contact-us-form">
    <div class="form-group">
        <label for="nameInputEmail1">Name</label>
        <input type="text" class="form-control" id="nameInputEmail1" name="name" placeholder="Full name">
    </div>
    <div class="form-group">
        <label for="exampleInputEmail1">Email address</label>
        <input type="email" class="form-control" id="exampleInputEmail1" name="email"
               placeholder="Enter email">
    </div>
    <div class="form-group">
        <label for="phoneInputEmail1">Phone number</label>
        <input type="text" class="form-control" id="phoneInputEmail1" name="phone"
               placeholder="Enter phone">
    </div>
    <div class="form-group">
        <label for="messageInputEmail1">Message</label>
        <textarea type="textarea" class="form-control" id="messageInputEmail1" name="message"
                  placeholder="Enter message"></textarea>
    </div>
    <p class="thanks">Thanks!  We'll contact you soon.</p>
    <button type="submit" class="btn btn-primary g-recaptcha"
      data-sitekey="6LdrWS0UAAAAAPAokGKpRhrObJkaaCX0EMsEiofN"
      data-callback="onContctUsSubmit" data-badge="inline" >Submit</button>
</form>

$.post($("#contact-us-form").attr('action'), JSON.stringify({
    name: $("#contact-us-form input[name='name']").val(),
    email: $("#contact-us-form input[name='email']").val(),
    phone: $("#contact-us-form input[name='phone']").val(),
    message: $("#contact-us-form textarea[name='message']").val(),
    'g-recaptcha-response': $("#contact-us-form textarea[name='g-recaptcha-response']").val()
}), function (data) {
    $(".thanks").show();
    $("#contact-us-form button").hide();
}, 'json');