add postgres and refactor code

config/config.go

@@ -17,7 +17,7 @@ func New() *Config {
 	return &Config{
 		Server: ServerConfig{
 			Port:             getEnv("PORT", "8080"),
-			ConnectionString: getEnv("CONNECTION_STRING", "test.db"),
+			ConnectionString: getEnv("CONNECTION_STRING", "host=localhost user=astra_users password=password dbname=astra_users_db port=5432 sslmode=disable TimeZone=Europe/Moscow"),
 		},
 	}
 }