如何在dotnet core3.1 MacOS上使用ECDsa对已有私钥的消息进行签名？

using System;
using System.Security.Cryptography;
using System.Text;

string privateKey = "your_private_key_here";
byte[] privateKeyBytes = Convert.FromBase64String(privateKey);

using (ECDsa ecdsa = ECDsa.Create())
{
    ecdsa.ImportPkcs8PrivateKey(privateKeyBytes, out _);
    
    // 进行签名操作
}

string message = "your_message_here";
byte[] messageBytes = Encoding.UTF8.GetBytes(message);

byte[] signature = ecdsa.SignData(messageBytes, HashAlgorithmName.SHA256);

string signatureBase64 = Convert.ToBase64String(signature);