go-sample-webpage/pkg/user/templates/login.tmpl

{{if .msg}}
<div class="alert alert-warning" role="alert">
    {{ .msg }}
</div>
{{end}}
<form method="post">
<div class="form-floating mb-3">
    <input type="text" name="username" class="form-control" id="floatingInput" value="{{ .username }}" placeholder="Username"/>
    <label for="floatingInput">Username</label>
</div>
<div class="form-floating mb-3">
    <input type="password" name="password"  class="form-control" id="floatingInput" placeholder="Password">
    <label for="floatingInput">Password</label>
</div>
<input type="text" name="captchaid" style="display: none"  class="form-control" id="floatingInput" value="{{ .captcha }}" />
<div class="row">
    <div class="col-md-3">
        <img src="/captcha/{{ .captcha }}.png" style="height: 56px;"></img>
    </div>

    <div class="col-md-9">
        <div class="form-floating mb-3">
            <input type="text" name="captcha"  class="form-control" id="floatingInput" placeholder="Captcha code">
            <label for="floatingInput">Captcha code</label>
        </div>
    </div>
</div>
    <input type="submit" class="btn btn-success" value="Login"></input>
</form>