type levelFilterCore … var _ … var _ … // NewIncreaseLevelCore creates a core that can be used to increase the level of // an existing Core. It cannot be used to decrease the logging level, as it acts // as a filter before calling the underlying core. If level decreases the log level, // an error is returned. func NewIncreaseLevelCore(core Core, level LevelEnabler) (Core, error) { … } func (c *levelFilterCore) Enabled(lvl Level) bool { … } func (c *levelFilterCore) Level() Level { … } func (c *levelFilterCore) With(fields []Field) Core { … } func (c *levelFilterCore) Check(ent Entry, ce *CheckedEntry) *CheckedEntry { … } func (c *levelFilterCore) Write(ent Entry, fields []Field) error { … } func (c *levelFilterCore) Sync() error { … }