func errorHandler(err error, c *echo.Context) {
code := http.StatusInternalServerError
msg := http.StatusText(code)
if he, ok := err.(*echo.HTTPError); ok {
code = he.Code()
msg = he.Error()
}
c.Response().Header().Set("Content-Type", "text/plain; charset=utf-8")
c.Response().WriteHeader(code)
c.Response().Write([]byte(msg))
}