package fetchuser import ( "encoding/json" "fmt" "io" "net/http" ) type User struct { ID int `json:"id"` Name string `json:"name"` } type APIFetcher interface { FetchData(id int) (User, error) } type RealAPIFetcher struct { ApiURL string } func (ra *RealAPIFetcher) FetchData(id int) (User, error) { resp, err := http.Get(fmt.Sprintf("%s/users/%d", ra.ApiURL, id)) if err != nil { return User{}, err } defer resp.Body.Close() bodyBytes, err := io.ReadAll(resp.Body) if err != nil { return User{}, err } var user User err = json.Unmarshal(bodyBytes, &user) return user, err } func ProcessUser(fetcher APIFetcher, id int) (User, error) { user, err := fetcher.FetchData(id) if err != nil { return User{}, err } // Process the user data. return user, nil }