Improving EncoderStream to return error only upon non io.EOF.

io.EOF is okay since io.ReadFull will not have read any bytes at all.

Also making error channel receive only for go routine.

pkg/donut/bucket.go

@@ -447,14 +447,13 @@ func (b bucket) writeObjectData(k, m uint8, writers []io.WriteCloser, objectData
 		}
 		for blockIndex, block := range encodedBlocks {
 			errCh := make(chan error, 1)
-			go func(writer io.Writer, reader io.Reader) {
-				// FIXME: this closes the errCh in the outer scope
+			go func(writer io.Writer, reader io.Reader, errCh chan<- error) {
 				defer close(errCh)
 				_, err := io.Copy(writer, reader)
 				errCh <- err
-			}(writers[blockIndex], bytes.NewReader(block))
+			}(writers[blockIndex], bytes.NewReader(block), errCh)
 			if err := <-errCh; err != nil {
-				// FIXME: fix premature return in case of err != nil
+				// Returning error is fine here CleanupErrors() would cleanup writers
 				return 0, 0, iodine.New(err, nil)
 			}
 		}