fix:refactor unused functions in concrete builder

Author: Mohamed

designpatterns/builder/builderinterface.go

@@ -9,11 +9,11 @@ type iBuilder interface {
 
 func getBuilder(builderType string) iBuilder {
 	if builderType == "normal" {
-		return &normalBuilder{}
+		return newNormalBuilder()
 	}
 
 	if builderType == "igloo" {
-		return &iglooBuilder{}
+		return newIglooBuilder()
 	}
 	return nil
 }