token-create.cs

public string CreateToken(User user)
        {
            if (user == null)
                throw new ArgumentException(nameof(user));

            var claims = new[]
            {
                new Claim(ClaimTypes.NameIdentifier, user.Username)
            };

            var key = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(_configuration["JwtKey"]));
            var creds = new SigningCredentials(key, SecurityAlgorithms.HmacSha256Signature);

            var token = new JwtSecurityToken(_configuration["JwtIssuer"],
                _configuration["JwtAudience"],
                claims,
                expires: DateTime.Now.AddMonths(1),
                signingCredentials: creds);

            return new JwtSecurityTokenHandler().WriteToken(token);
        }