Moving away from goamz to use minio-go instead. (#4193)

minio-go does fully managed way of handling S3 API requests

  - Automatic bucket location management across all s3 regions.
  - Transparently upload large files in multipart if file 64MB
    or larger.
  - Right GetObject() API provides compatibility with
    io.ReadWriteSeeker interface.
  - Various other APIs including bulk deletes, server side object
    copy, bucket policies and bucket notifications.

Fixes #4182

vendor/github.com/minio/minio-go/hook-reader.go

@@ -0,0 +1,70 @@
+/*
+ * Minio Go Library for Amazon S3 Compatible Cloud Storage (C) 2015, 2016 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package minio
+
+import "io"
+
+// hookReader hooks additional reader in the source stream. It is
+// useful for making progress bars. Second reader is appropriately
+// notified about the exact number of bytes read from the primary
+// source on each Read operation.
+type hookReader struct {
+	source io.Reader
+	hook   io.Reader
+}
+
+// Seek implements io.Seeker. Seeks source first, and if necessary
+// seeks hook if Seek method is appropriately found.
+func (hr *hookReader) Seek(offset int64, whence int) (n int64, err error) {
+	// Verify for source has embedded Seeker, use it.
+	sourceSeeker, ok := hr.source.(io.Seeker)
+	if ok {
+		return sourceSeeker.Seek(offset, whence)
+	}
+	// Verify if hook has embedded Seeker, use it.
+	hookSeeker, ok := hr.hook.(io.Seeker)
+	if ok {
+		return hookSeeker.Seek(offset, whence)
+	}
+	return n, nil
+}
+
+// Read implements io.Reader. Always reads from the source, the return
+// value 'n' number of bytes are reported through the hook. Returns
+// error for all non io.EOF conditions.
+func (hr *hookReader) Read(b []byte) (n int, err error) {
+	n, err = hr.source.Read(b)
+	if err != nil && err != io.EOF {
+		return n, err
+	}
+	// Progress the hook with the total read bytes from the source.
+	if _, herr := hr.hook.Read(b[:n]); herr != nil {
+		if herr != io.EOF {
+			return n, herr
+		}
+	}
+	return n, err
+}
+
+// newHook returns a io.ReadSeeker which implements hookReader that
+// reports the data read from the source to the hook.
+func newHook(source, hook io.Reader) io.Reader {
+	if hook == nil {
+		return source
+	}
+	return &hookReader{source, hook}
+}