How to create FIRUser with sign in with custom token?
<p>I am using it for iOS in Swift programming language!</p>

<ul>
<li><p>I am using Firebase for my Backend stuff</p></li>
<li><p>I am using Facebook account kit for log in. </p>

<ul>
<li>I am getting Account kit access token</li>
</ul></li>
</ul>

<p>So I basically use Account kit access token </p>

<pre><code>FIRAuth.auth()?.signInWithCustomToken(accessToken.tokenString, completion: { (user, error) in
        print(user)
        print("\n\n\n\(error)")
    })
</code></pre>

<p>I get error in console that </p>

<p><strong>"Error Domain=FIRAuthErrorDomain Code=17000 "The custom token format is incorrect. Please check the documentation." UserInfo={NSLocalizedDescription=The custom token format is incorrect. Please check the documentation., error_name=ERROR_INVALID_CUSTOM_TOKEN})"</strong></p>

<p>Reference to the Firebase <a href="https://firebase.google.com/docs/auth/ios/custom-auth#authenticate-with-firebase" rel="nofollow">click here!</a></p>