[#276] Merge repo with frostfs-api-go

Signed-off-by: Pavel Pogodaev <p.pogodaev@yadro.com>

api/rpc/client/conn.go

@@ -0,0 +1,24 @@
+package client
+
+import (
+	"io"
+
+	"google.golang.org/grpc"
+)
+
+// Conn is an interface for grpc client connection.
+type Conn interface {
+	grpc.ClientConnInterface
+	io.Closer
+}
+
+// Conn returns underlying connection.
+//
+// Returns non-nil result after the first Init() call
+// completed without a connection error.
+//
+// Client should not be used after Close() call
+// on the connection: behavior is undefined.
+func (c *Client) Conn() io.Closer {
+	return c.conn
+}