Proper use of retrofit

In general, I found such an example on the net: retrofit

When connecting, the following difficulties arose:

error 2:

tell me what am I doing wrong?

interface:

public interface GithubAPI { @GET("/users/{username}") Call<GithubUser> getUser(@Path("username") String username); @GET("/users/{username}") Call<GithubUser> getId(@Path("id") int id); 

}