PostsController.cs

private readonly IPostService _postService;

public PostsController(IPostService postService) {
  _postService = postService;
}

[HttpGet(ApiRoutes.Posts.Get)]
public IActionResult Get([FromRoute] Guid postId)
{
  var post = _postService.GetPostById(postId);

  if (post == null)
    return NotFound();
  
  return Ok(post);
}