Enhance guidance for go proxy server in Dependabot (#40382)

Co-authored-by: Sharra-writes <[email protected]>
Co-authored-by: Copilot <[email protected]>

Author: 3 people

content/code-security/dependabot/working-with-dependabot/guidance-for-the-configuration-of-private-registries-for-dependabot.md

@@ -270,10 +270,16 @@ GONOSUMDB=my-company.com/*
 
 #### Notes
 
-{% data reusables.dependabot.access-private-dependencies-link %}
-
 This feature enables unified dependency management for both public and private Go modules within a single {% data variables.product.prodname_dependabot %} workflow, making it ideal for organizations using corporate artifact management systems like JFrog Artifactory or Nexus.
 
+**Private Proxy Serving All Modules**: All module requests go through your proxy first. For public modules fetching failures, your proxy returns 404/410 and Go falls back to direct version control system (VCS) access. For private modules, such as those published only to a private repository like JFrog Artifactory, the VCS fall back will not work since they are only accessible through the proxy.
+
+**Private Proxy Serving Private Modules**: Add a go.env to your repository root, and set up a GONOSUMDB matching the private modules pattern (for example, `GONOSUMDB=my-company.com/*` for all private modules starting with my-company.com/). Doing this will disable the public checksum validation of your private modules because the public checksum database does not have those private modules.
+
+**Direct Access to Private Modules**: Set `GOPRIVATE=my-company.com/*` to bypass proxies and fetch directly from VCS. This setting only works if private modules are properly published with semantic version tags in your source control.
+
+{% data reusables.dependabot.access-private-dependencies-link %}
+
 ### Maven
 
 Maven supports username and password authentication. For more information, see `maven-repository` in [AUTOTITLE](/code-security/dependabot/working-with-dependabot/configuring-access-to-private-registries-for-dependabot#maven-repository).