Unable to set query parameters manually for a rest api (using mux)

Question

I am implementing a Rest api using mux. After validating some parameters, I am trying to fill the missing parameters with some default values which I process later by the method that handles the request, however, I noticed that setting query parameters manually does not have any effect, unless the raw query is directly changed which is a bit hacky:

func ValidateParameters(r *http.Request) (bool) {

     test := r.URL.Query().Get("test")

   // if test is not provided set some default value

    if test == "" {

        r.URL.Query().Set("test", "Test1") //not working
        r.URL.Query().Add("test", "Test2") //not working
        r.URL.RawQuery = r.URL.RawQuery + "&Test=Test3" // the only method working

     }

       // more code

}

The handler is in another file, so I want to be able to do test := r.URL.Query().Get("test") and get the value that I set inside ValidateParameters which is called by the request handler, but this is not working.

any explanation to that ? any way to work around it ?

Thanks.

Answer 1

The problem is that r.URL.Query() parses the url, creates the map of parameters and returns it. This is done with every .Query() call.

This should work:

params := r.URL.Query()
params.Set("key", "value")
r.URL.RawQuery = params.Encode()