gistfile1.txt

var tokenValidationParameters = new TokenValidationParameters
{
    ValidateIssuerSigningKey = true,
    IssuerSigningKey = new SymmetricSecurityKey(Encoding.ASCII.GetBytes(jwtSettings.Secret)),
    ValidateIssuer = false,
    ValidateAudience = false,
    RequireExpirationTime = false,
    ValidateLifetime = true
};

services.AddSingleton(tokenValidationParameters);

services.AddAuthentication(x =>
    {
        // ...
    })
    .AddJwtBearer(x =>
    {
        x.SaveToken = true;
        x.TokenValidationParameters = tokenValidationParameters;
    });