How can I test the connection string quickly to verify it is the cause of the 'panic error parsing uri scheme' error?

Use a MongoDB client tool like `mongosh` (the MongoDB Shell) or a GUI tool like MongoDB Compass. Try connecting to your database using the exact same connection string you are using in your application. If you can successfully connect via these tools, the connection string itself is likely correct, and the issue could stem from the way it's being provided to your application (e.g., incorrect environment variable or faulty code).