Simplify data verification with HashReader. (#5071)

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.

cmd/test-utils_test.go

@@ -53,6 +53,7 @@ import (
 	"github.com/fatih/color"
 	router "github.com/gorilla/mux"
 	"github.com/minio/minio-go/pkg/s3signer"
+	"github.com/minio/minio/pkg/hash"
 )
 
 // Tests should initNSLock only once.
@@ -129,6 +130,14 @@ func calculateSignedChunkLength(chunkDataSize int64) int64 {
 		2 // CRLF
 }
 
+func mustGetHashReader(t TestErrHandler, data io.Reader, size int64, md5hex, sha256hex string) *hash.Reader {
+	hr, err := hash.NewReader(data, size, md5hex, sha256hex)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return hr
+}
+
 // calculateSignedChunkLength - calculates the length of the overall stream (data + metadata)
 func calculateStreamContentLength(dataLen, chunkSize int64) int64 {
 	if dataLen <= 0 {
@@ -1975,6 +1984,7 @@ func ExecObjectLayerTest(t TestErrHandler, objTest objTestType) {
 	if err != nil {
 		t.Fatalf("Initialization of object layer failed for single node setup: %s", err)
 	}
+
 	// Executing the object layer tests for single node setup.
 	objTest(objLayer, FSTestStr, t)