You don't have to use the full url to import a package. The name of a git repository doesn't have to match the remote name though, so I don't see why it would be a problem to fork a repository.
Echo is using some imports to their own packages inside the project.
IE: https://github.com/labstack/echo/blob/a098bcd3b0c445dde3d380...
So if I fork "echo", I have to replace the urls in their imports so it imports my fork packages.