JwtTokenBuilder.cs

public string Build()
{
    var claims = new List<Claim>
    {
      new Claim(JwtRegisteredClaimNames.Sub, this.subject),
      new Claim(JwtRegisteredClaimNames.Jti, Guid.NewGuid().ToString()),
      new Claim("NameId", this.nameId)
    }
    .Union(this.claims.Select(item => new Claim(item.Key, item.Value)));

    var token = new JwtSecurityToken(
                      issuer: this.issuer,
                      audience: this.audience,
                      claims: claims,
                      expires: DateTime.UtcNow.AddMinutes(expiryInMinutes),
                      signingCredentials: new SigningCredentials(
                                                this.securityKey,
                                                SecurityAlgorithms.HmacSha256));

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