logger := log.NewLogfmtLogger(os.Stderr)
logger = log.NewContext(logger).With("caller", log.DefaultCaller)
lvlLogger := levels.New(logger)
lvlLogger.Info("hi", "there")

In the output you will get: caller=levels.go:72

This is fixed by using log.Caller(4) instead of log.DefaultCaller but makes passing and extending the logger harder than it should be.