[Route("api/[controller]")]
public class AuthenticateController : Controller
{
    [HttpPost]
    [Route("login")]
    public IActionResult Login([FromBody]LoginInput input)
    {
        //从数据库验证用户名，密码
        //验证通过 否则 返回Unauthorized
        //创建claim
        var authClaims = new[] {
            new Claim(JwtRegisteredClaimNames.Sub,input.Username),
            new Claim(JwtRegisteredClaimNames.Jti,Guid.NewGuid().ToString())
        };
        IdentityModelEventSource.ShowPII = true;
        //签名秘钥 可以放到json文件中
        var authSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes("SecureKeySecureKeySecureKeySecureKeySecureKeySecureKey"));
        var token = new JwtSecurityToken(
               issuer: "https://www.cnblogs.com/chengtian",
               audience: "https://www.cnblogs.com/chengtian",
               expires: DateTime.Now.AddHours(2),
               claims: authClaims,
               signingCredentials: new SigningCredentials(authSigningKey, SecurityAlgorithms.HmacSha256)
               );
        //返回token和过期时间
        return Ok(new
        {
            token = new JwtSecurityTokenHandler().WriteToken(token),
            expiration = token.ValidTo
        });
    }
}