Specified language version is too high error while compiling a dart project to executable

Question

I am compiling dart file to exe, following is the code,

import 'dart:convert';
import 'dart:io';
import 'dart:typed_data';

import 'package:cryptography/cryptography.dart';
main() async {
  var server=await HttpServer.bind(InternetAddress.loopbackIPv4, 8080);
  server.listen((event) {
    if(event.uri=="/getSecret")
      {
        utf8.decodeStream(event).then((value) {
          var json= jsonDecode(value);
          var clientpublickey= json['clientkey'];
          var algorithm=Diffie.getAlgorithm();
          Diffie.getKeyPair(algorithm).then((keys) {
            keys.extractPublicKey().then((publicKey){
              var serverpublickey=base64Encode(publicKey.bytes);
              Diffie.computeSecret(algorithm, keys, SimplePublicKey(List.from(Uint8List.fromList(base64Decode(clientpublickey))).cast<int>(), type: algorithm.keyPairType)).then((secret) {
                event.response.write({
                  "secret":secret,
                  "serverpublickey":serverpublickey,
                });
                event.response.close();
              });
            });
          });
        });
      }
    else
      {
        event.response.write({
          "result": false,
          "error": "Invalid url."
        });
        event.response.close();
      }
  });
}
class Diffie {
  static X25519 getAlgorithm()
  {
    return X25519();
  }
  static Future<SimpleKeyPair> getKeyPair(X25519 algorithm) async
  {
    return await algorithm.newKeyPair();
  }
  static Future<SimplePublicKey> getPublickey(SimpleKeyPair simpleKeyPair) async
  {
    return await simpleKeyPair.extractPublicKey();
  }
  static Future<String> computeSecret(X25519 algorithm, SimpleKeyPair keyPair, SimplePublicKey remotePublicKey) async
  {
    return base64Encode(await (await algorithm.sharedSecretKey(keyPair: keyPair, remotePublicKey: remotePublicKey)).extractBytes());
  }
}

I am using 'cryptography' plugin here. When i try to compile I get the following error

bin/main.dart:1:1: Error: The specified language version is too high. The highest supported language version is 2.10.

What should i do? I am building a dart server. I intend to upload this file to git and send it to ec2 linux server and run it as dart could not be installed on linux ec2 instance. Please help.