As I center this button inside a nav-item, the html looks like this:
<nav class="navbar navbar-expand-sm bg-light navbar-light sticky-top">
<div class="container">
<a class="navbar-brand" href="#">
<img src="imgs/logocompleto.png">
</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarResponsive" aria-controls="navbarResponsive" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarResponsive">
<ul class="navbar-nav ml-auto">
<li class="nav-item active">
<a class="nav-link" href="#">Home
<span class="sr-only">(current)</span>
</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">About</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Services</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Contact</a>
</li>
<li class="nav-item">
<button type="button" class="align-middle" data-toggle="modal" data-target="#myModal">
Começe Agora
</button>
</li>
</ul>
</div>
</div>
</nav>
I'm using bootstrap 4