title: I've got into an error while connecting to mongodb and express and my terminal's gone mad
body: <p>Here's the error. It's blowing me up. Please help.</p>
  <p>It's just getting mad at me for something that is not supported. And it's shouting at me not supported. I've never seen that many errors in the terminal. Can anyone tell me why I am getting this.</p>
  <pre><code>  DeprecationWarning: current Server Discovery and Monitoring engine is 
  
  deprecated, and will be removed in a future version. To use the new Server Discover and Monitoring engine, pass option { useUnifiedTopology: true } to the MongoClient constructor.
  Server running on port 300
  (node:6452) UnhandledPromiseRejectionWarning: MongooseError: Can't call `openUri()` on an active connection with different connection strings. Make sure you aren't calling `mongoose.connect()` multiple times. See: https://mongoosejs.com/docs/connections.html#multiple_connections    at NativeConnection.Connection.openUri (C:\Users\hp\Documents\short shortnner-backend\node_modules\mongoose\lib\connection.js:682:13)
      at C:\Users\hp\Documents\short shortnner-backend\node_modules\mongoose\lib\index.js:342:10
      at C:\Users\hp\Documents\short shortnner-backend\node_modules\mongoose\lib\helpers\promiseOrCallback.js:31:5
      at new Promise (&lt;anonymous&gt;)
      at promiseOrCallback (C:\Users\hp\Documents\short shortnner-backend\node_modules\mongoose\lib\helpers\promiseOrCallback.js:30:10)
      at Mongoose.connect (C:\Users\hp\Documents\short shortnner-backend\node_modules\mongoose\lib\index.js:341:10)
      at Object.&lt;anonymous&gt; (C:\Users\hp\Documents\short shortnner-backend\models\Url.js:10:27)    at Module._compile (internal/modules/cjs/loader.js:1138:30)
      at Object.Module._extensions..js (internal/modules/cjs/loader.js:1158:10)
      at Module.load (internal/modules/cjs/loader.js:986:32)
      at Function.Module._load (internal/modules/cjs/loader.js:879:14)
      at Module.require (internal/modules/cjs/loader.js:1026:19)
      at require (internal/modules/cjs/helpers.js:72:18)
      at Object.&lt;anonymous&gt; (C:\Users\hp\Documents\short shortnner-backend\routes\url.js:7:13) 
      at Module._compile (internal/modules/cjs/loader.js:1138:30)
      at Object.Module._extensions..js (internal/modules/cjs/loader.js:1158:10)
  (node:6452) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
  (node:6452) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code. DeprecationWarning: current Server Discovery and Monitoring engine is deprecated, and will be removed in a future version. To use the new Server Discover and Monitoring engine, pass option { useUnifiedTopology: true } to the MongoClient constructor.
  Server running on port 300
  (node:6452) UnhandledPromiseRejectionWarning: MongooseError: Can't call `openUri()` on an active connection with different connection strings. Make sure you aren't calling `mongoose.connect()` multiple times. See: https://mongoosejs.com/docs/connections.html#multiple_connections    at NativeConnection.Connection.openUri (C:\Users\hp\Documents\short shortnner-backend\node_modules\mongoose\lib\connection.js:682:13)
      at C:\Users\hp\Documents\short shortnner-backend\node_modules\mongoose\lib\index.js:342:10
      at C:\Users\hp\Documents\short shortnner-backend\node_modules\mongoose\lib\helpers\promiseOrCallback.js:31:5
      at new Promise (&lt;anonymous&gt;)
      at promiseOrCallback (C:\Users\hp\Documents\short shortnner-backend\node_modules\mongoose\lib\helpers\promiseOrCallback.js:30:10)
      at Mongoose.connect (C:\Users\hp\Documents\short shortnner-backend\node_modules\mongoose\lib\index.js:341:10)
      at Object.&lt;anonymous&gt; (C:\Users\hp\Documents\short shortnner-backend\models\Url.js:10:27)    at Module._compile (internal/modules/cjs/loader.js:1138:30)
      at Object.Module._extensions..js (internal/modules/cjs/loader.js:1158:10)
      at Module.load (internal/modules/cjs/loader.js:986:32)
      at Function.Module._load (internal/modules/cjs/loader.js:879:14)
      at Module.require (internal/modules/cjs/loader.js:1026:19)
      at require (internal/modules/cjs/helpers.js:72:18)
      at Object.&lt;anonymous&gt; (C:\Users\hp\Documents\short shortnner-backend\routes\url.js:7:13) 
      at Module._compile (internal/modules/cjs/loader.js:1138:30)
      at Object.Module._extensions..js (internal/modules/cjs/loader.js:1158:10)
  (node:6452) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
  (node:6452) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
   MongoDB Connected...
  </code></pre>
  <p>Here's the link to my <a href="https://github.com/dingus45191/short-shortnner-backend" rel="nofollow noreferrer">code</a></p>