Thank you, I saw this post, but it took me a bit of time to understand the point and try a lot of possibilities.
So I had something wrong, and that didn't work.
After a good setup, and doing the "reload and run", I had the following message : "Unable to read data from the transport connection: The connection was closed."
But at least, that was one step.
After trying to figure out what is the problem with my header "Connection : keep-alive", I tried this just like that, to see what happens :
And now, I have an endpoint error but it's because I think I'm wrong on how are working the parameters in the path.
So my initial problem is resolved, thank you for your answer !