add retries request

Signed-off-by: Emile Vauge <emile@vauge.com>

configuration.go

@@ -27,6 +27,7 @@ type GlobalConfiguration struct {
 	DefaultEntryPoints        DefaultEntryPoints
 	ProvidersThrottleDuration time.Duration
 	MaxIdleConnsPerHost       int
+	Retry                     *Retry
 	Docker                    *provider.Docker
 	File                      *provider.File
 	Web                       *WebProvider
@@ -182,6 +183,12 @@ type Certificate struct {
 	KeyFile  string
 }
 
+// Retry contains request retry config
+type Retry struct {
+	Attempts int
+	MaxMem   int64
+}
+
 // NewGlobalConfiguration returns a GlobalConfiguration with default values.
 func NewGlobalConfiguration() *GlobalConfiguration {
 	return new(GlobalConfiguration)