config.go: externalize config preparation for more convenient testing

config.go

@@ -47,6 +47,10 @@ func LoadConfig(path string) (*Config, error) {
 		return nil, err
 	}
 
+	return prepareConfig(&cfg)
+}
+
+func prepareConfig(cfg *Config) (*Config, error) {
 	// temporary map for preventing duplicate records between users
 	records := make(map[string]bool)
 
@@ -85,5 +89,6 @@ func LoadConfig(path string) (*Config, error) {
 		}
 		cfg.rrconfigs[record.Recordname] = &record
 	}
-	return &cfg, nil
+
+	return cfg, nil
 }