Fix env var name

Author: sadikkuzu

README.md

@@ -6,7 +6,7 @@ It was written to accompany a [blog post](https://developer.mongodb.com/quicksta
 ## TL;DR
 
 If you really don't want to read the [blog post](https://developer.mongodb.com/quickstart/python-quickstart-fastapi/) and want to get up and running,
-activate your Python virtualenv, and then run the following from your terminal (edit the `DB_URL` first!):
+activate your Python virtualenv, and then run the following from your terminal (edit the `MONGODB_URL` first!):
 
 ```bash
 # Install the requirements:
@@ -23,4 +23,4 @@ uvicorn app:app --reload
 
 Now you can load http://localhost:8000 in your browser ... but there won't be much to see until you've inserted some data.
 
-If you have any questions or suggestions, check out the [MongoDB Community Forums](https://developer.mongodb.com/community/forums/)!
+If you have any questions or suggestions, check out the [MongoDB Community Forums](https://developer.mongodb.com/community/forums/)!