部署了App Engine Standard [Nodejs]，并收到PORT env错误

Question

我已将应用程序部署到GAE，但日志中出现错误，导致构建中断。我将端口设置为8080，例如：

const port = dev ? 3000 : 8080

碰巧我因为其他原因得到了500错误，但这也在日志中。

start: Cannot start nginx. Performance may be degraded. Fallback mechanism is unsupported and may be removed at any time. App should listen on PORT environment variable. Fallback engaged: app is listening on port 8080