I don't know much about Google map, what do you mean by key value, is it an API key?
Do you have to use Google map? SSRS comes with maps that integrated feature with bing maps, Spatial data etc. I recommend you use these. You can see this link: https://learn.microsoft.com/en-us/sql/reporting-services/report-design/maps-report-builder-and-ssrs?view=sql-server-ver16.
Best regards,
Aniya