Amazon S3 SDK在某些编程语言中可能不允许直接使用同步方法，例如GetObjectMetadata方法。相反，它要求您使用异步方法GetObjectMetadataAsync来执行此操作。以下是一个使用GetObjectMetadataAsync方法的代码示例：

Java:

import software.amazon.awssdk.services.s3.S3AsyncClient;
import software.amazon.awssdk.services.s3.model.GetObjectMetadataRequest;
import software.amazon.awssdk.services.s3.model.GetObjectMetadataResponse;

public class S3Example {
    public static void main(String[] args) {
        S3AsyncClient s3Client = S3AsyncClient.create();
        
        GetObjectMetadataRequest request = GetObjectMetadataRequest.builder()
                .bucket("your-bucket-name")
                .key("your-object-key")
                .build();
        
        s3Client.getObjectMetadata(request)
                .whenComplete((response, exception) -> {
                    if (response != null) {
                        // 处理GetObjectMetadataResponse
                        System.out.println("ETag: " + response.eTag());
                        System.out.println("Content-Type: " + response.contentType());
                    } else {
                        // 处理异常
                        System.out.println("Error: " + exception.getMessage());
                    }
                })
                .join(); // 等待异步操作完成
    }
}

Python:

import asyncio
import aiobotocore

async def main():
    async with aiobotocore.create_client('s3') as s3_client:
        response = await s3_client.head_object(
            Bucket='your-bucket-name',
            Key='your-object-key'
        )
        
        # 处理GetObjectResponse
        print("ETag:", response['ETag'])
        print("Content-Type:", response['Content-Type'])

loop = asyncio.get_event_loop()
loop.run_until_complete(main())

请注意，示例代码中的"your-bucket-name"和"your-object-key"应替换为您实际使用的S3存储桶名称和对象键。