func CallerKey() interface{} {
	return callerKey
}
CallerKey returns the logging key to be used for the stack location of the logging call
package logging
import (
	"os"
	"strings"
	"github.com/go-kit/kit/log"
	"github.com/go-kit/kit/log/level"
)
var (
	defaultLogger = log.NewJSONLogger(log.NewSyncWriter(os.Stdout))
	callerKey    interface{} = "caller"
	messageKey   interface{} = "msg"
	errorKey     interface{} = "error"
	timestampKey interface{} = "ts"
)