JwtSecurityToken .NET 8

Question

I just have seen this post but it is not completely what I need...

I have seen that with Core 8 I don't get no more a success response when I call API function with this code:

var claims = new[]
{
    new Claim(JwtRegisteredClaimNames.Sub, user.UserName),
    new Claim(JwtRegisteredClaimNames.Jti, Guid.NewGuid().ToString()),
    new Claim(ClaimTypes.Role, "Administrator")
};

var token = new JwtSecurityToken(
    issuer: "http://portaleWeb.com",
    audience: "http://portaleWeb.com",
    expires: DateTime.UtcNow.AddHours(1),
    claims: claims,
    signingCredentials: new SigningCredentials(signingKey, SecurityAlgorithms.HmacSha256));

return Ok(new
{
    token = new JwtSecurityTokenHandler().WriteToken(token),
    expiration = token.ValidTo
});

I read that now the object is a JsonWebToken, but don't know how to change the code... Someone that can help me?