Package logging defines Logger interface and context.Context helpers to put\get logger from context.Context.
Unfortunately standard library doesn't define any Logger interface (only struct). And even worse: GAE logger is exposing different set of methods. Some additional layer is needed to unify the logging. Package logging is intended to be used from packages that support both local and GAE environments. Such packages should not use global logger but must accept instances of Logger interface (or even more generally context.Context) as parameters. Then callers can pass appropriate Logger implementation (or inject appropriate logger into context.Context) depending on where the code is running.