URGENT MAJOR - Update data-source.md

[sahilrajput03]

Update file with appropriate necessary cache initialization for http requests. Without this, the error is throws like: fetch is undefined.

[sahilrajput03]

Can anybody please tell whats the status of this issue, I guess this is something really important coz the program throws errror as fetch is undeifined, and there's no clue on how to deal with it.