I am running tests on selenium grid using nunit C# with:
- selenium-standalone-server: v3.3.1
- selenium webdriver: v3.3
- geckodriver: 0.15
- firefox: v52
Firefox is not installed on the default location and so I get following exception on running tests:
Expected browser binary location, but unable to find binary in default location, no 'moz:firefoxOptions.binary' capability provided, and no binary flag set on the command line (WARNING: The server did not provide any stacktrace information)
I want to specify Firefox executable path on the capabilities section of node.config file of selenium grid. How do I do that with new geckodriver? 
firefox_binary is now obsolete and it uses "moz:firefoxOptions", but I don't know how to specify it in selenium node's config file.
This is what I am doing in the config file, but its not working:
{
  "capabilities":
  [
    {
      "platform": "WINDOWS",
      "browserName": "firefox",
      "moz:firefoxOptions": {
        "binary": "D:\\Browsers\\Mozilla Firefox\\firefox.exe"
        },
      "maxInstances": 1,
      "seleniumProtocol": "WebDriver"
    }
  ]
.........
