Verify() was being called by caller after the data
has been successfully read after io.EOF. This disconnection
opens a race under concurrent access to such an object.
Verification is not necessary outside of Read() call,
we can simply just do checksum verification right inside
Read() call at io.EOF.
This approach simplifies the usage.
Content-Encoding is set to "aws-chunked" which is an S3 specific
API value which is no meaning for an object. This is how S3
behaves as well for a streaming signature uploaded object.
* Refactor streaming signatureV4 w/ state machine
- Used state machine to make transitions between reading chunk header,
chunk data and trailer explicit.
* debug: add print/panic statements to gather more info on CI failure
* Persist lastChunk status between Read() on ChunkReader
... remove panic() which was added as interim aid for debugging.
* Add unit-tests to cover v4 streaming signature
