vscode API client that doesn't charge for OAuth2.0?

If you're looking for a free API client extension for VSCode that supports OAuth2.0, check out EchoAPI. It's a solid alternative to Postman.

Thunder Client is also popular, but some OAuth2.0 features require a paid upgrade. EchoAPI gives you that functionality for free.

check the following article 

https://dev.to/patrick_61cbc6392b72286f6/the-best-thunder-client-alternative-free-echoapi-for-vscode-53hm