title: Streaming uploading to S3 using presigned URL
body: <p>I'm trying to upload a file into a customer's S3. I'm given a presigned URL that allows me to do a <code>PUT</code> request. I have no access to their access and secret key so the use of the AWS SDK is out of the question.</p>
  <p>The use case is that I am consuming a gRPC server streaming call and transforming it into a csv with some field changes. As the calls come in, I would want to be able to stream the transformed gRPC response into S3. I would need to do it via streaming cause the response can get rather large, upwards of &gt;100mb, so loading everything into memory before uploading it into S3 is not ideal. Any ideas?</p>