Plugin cannot upload to AWS sFTP

[mattzuba]

I'm attempting to upload a file using this to an AWS Transfer sFTP instance and it fails with sftp: "Cannot open file in mode: CREATE|READ|TRUNCATE|WRITE" (SSH_FX_OP_UNSUPPORTED).

Looking into the sftp go pkg and searching issues there, this is due to the Create function opening the file with the READ flag, but AWS sFTP does not support this as is now documented.

Any chance this can either be fixed here or a setting added to support AWS sFTP?