Web gateway source scheduled with parameter

Hello, i have a report published in powerbi where the report is connecting to an api call to get some data. This api call is driven by a parameter inside the report.

When publishing this apicall has to be added to the gateway sources in order to be selected in connections.

I can see in settings the parameter set in the report but how can i set the datasource to user this parameter like

Data Source name : myService

Data Source Type: Web

URL: https://myService?myparam=5

Where 5 comes from the report as parameter. 

https://myService?param1=#MyPar

is not working when the parameter name is MyPar in the report with value 5.

I did try to fix the report using the relative path so i have a query like:

= Json.Document(Web.Contents("https://myServer/myservice/api",[RelativePath="docStatus",Query=[MyPar=Text.From(docId)]]))

Inside the powerbi desktop this works fine.

In the powerbi service it is asking to add it to gateway.

Then in the url it placed only 

"https://myServer/myservice/api" and then i have 404 error on checking connection to the gateway. the message is

"Unable to connect to the data source undefined."