Remove cast.

values/decoding/string_decode.go

@@ -61,14 +61,7 @@ func tryDecodeStringDictionary(
 		if err != nil {
 			return 0, err
 		}
-		// Close the underlying reader if it satisifies the `io.ReadCloser` iface.
-		rc, ok := reader.(io.ReadCloser)
-		if ok {
-			// NB(bodu): We don't need to propagate `Close` errors back up because there aren't any.
-			// We have two types of string readers. A bytes reader and a compress reader. The bytes reader
-			// doesn't implement the `io.Closer` iface and the compress reader has no errors when calling `Close`.
-			defer rc.Close()
-		}
+		defer reader.Close()
 		bytesRead, err := xproto.DecodeStringArray(reader, stringArrayProto, decodeBuf)
 		if err != nil {
 			return 0, err

values/decoding/varint_int_iterator.go

@@ -53,13 +53,6 @@ func (it *varintIntIterator) Err() error {
 func (it *varintIntIterator) Close() {
 	it.closed = true
 	it.err = nil
-	// Close the underlying reader if it satisifies the `io.ReadCloser` iface.
-	rc, ok := it.reader.(io.ReadCloser)
-	if ok {
-		// NB(bodu): We don't need to propagate `Close` errors back up because there aren't any.
-		// We have two types of string readers. A bytes reader and a compress reader. The bytes reader
-		// doesn't implement the `io.Closer` iface and the compress reader has no errors when calling `Close`.
-		rc.Close()
-	}
+	it.reader.Close()
 	it.reader = nil
 }