func LoggingMiddleware(logger log.Logger) ServiceMiddleware {
	return func(next Service) Service {
		return loggingMiddleware{next, logger}
	}
}
LoggingMiddleware takes a logger as a dependency and returns a ServiceMiddleware.
package greeterservice
import (
	"time"
	"github.com/go-kit/kit/log"
)
type ServiceMiddleware func(Service) Service