我是Mongodb的新手，运行mongo后，我得到了：
MongoDB shell version v4.2.1
connecting to: mongodb://127.0.0.1:27017/?compressors=disabled&gssapiServiceName=mongodb
2019-12-08T20:59:51.774+0100 E QUERY [js] Error: couldn't connect to server 127.0.0.1:27017, connection attempt failed: SocketException: Error connecting to 127.0.0.1:27017 :: caused by :: Connection refused :
connect@src/mongo/shell/mongo.js:341:17
@(connect):2:6
2019-12-08T20:59:51.775+0100 F - [main] exception: connect failed
2019-12-08T20:59:51.775+0100 E - [main] exiting with code 1
请帮忙！