Override Function from Another Module in Golang - go

Question

How do you override a function created in another module in Golang?
Module A
In one module I have the function NewPersonApiService, the full code is laid out as below:
package openapi
import (
"context"
"errors"
"net/http"
)
// PersonApiService is a service that implements the logic for the PersonApiServicer
// This service should implement the business logic for every endpoint for the PersonApi API.
// Include any external packages or services that will be required by this service.
type PersonApiService struct {
}
// NewPersonApiService creates a default api service
func NewPersonApiService() PersonApiServicer {
return &PersonApiService{}
}
// ShowPerson - Detail
func (s *PersonApiService) ShowPerson(ctx context.Context) (ImplResponse, error) {
// TODO - update ShowPerson with the required logic for this service method.
// Add api_person_service.go to the .openapi-generator-ignore to avoid overwriting this service implementation when updating open api generation.
//TODO: Uncomment the next line to return response Response(200, Person{}) or use other options such as http.Ok ...
//return Response(200, Person{}), nil
//TODO: Uncomment the next line to return response Response(0, Error{}) or use other options such as http.Ok ...
//return Response(0, Error{}), nil
return Response(http.StatusNotImplemented, nil), errors.New("ShowPerson method not implemented")
}
Module B
In a separate module I want to override this NewPersonApiService.
I can call this function in the other module by doing the following:
package main
import (
"log"
"net/http"
openapi "build/code/spec/src"
)
func main() {
log.Printf("Server started")
PersonApiService := openapi.NewPersonApiService()
PersonApiController := openapi.NewPersonApiController(PersonApiService)
router := openapi.NewRouter(PersonApiController)
log.Fatal(http.ListenAndServe(":8080", router))
}
But if I try to override the function I get compilation error, unresolved type for openapi, below is what I was attempting to do:
package main
import (
"context"
"log"
"net/http"
openapi "build/code/spec/src"
)
func main() {
log.Printf("Server started")
PersonApiService := openapi.NewPersonApiService()
PersonApiController := openapi.NewPersonApiController(PersonApiService)
router := openapi.NewRouter(PersonApiController)
log.Fatal(http.ListenAndServe(":8080", router))
}
func (s openapi.PersonApiService) ShowPerson(ctx context.Context) (openapi.ImplResponse, error) {
return openapi.Response(200, openapi.Person{}), nil
}
Below is an image of the compilation error
Additional Info:
I believe Module B is properly referencing Module A.
Module A's go.mod file reads as follows:
module build/code/spec
go 1.13
require github.com/go-chi/chi/v5 v5.0.3
Module B's go.mod file reads as follows:
module bakkt.com/boilerplate
go 1.19
replace build/code/spec => ./../build/generated/
require build/code/spec v0.0.0-00010101000000-000000000000
require github.com/go-chi/chi/v5 v5.0.3 // indirect

Answer 1

The solution was to implement the ShowPerson method in another module, you would need to create a new type that implements the PersonApiServicer interface and provides its own implementation of the ShowPerson method.
Running this in Module B worked and allowed me to change the response of the API call defined in Module A.
package main
import (
"context"
"log"
"net/http"
openapi "build/code/spec/src"
)
type MyPersonApiService struct{}
func NewMyPersonApiService() openapi.PersonApiServicer {
return &MyPersonApiService{}
}
func (s *MyPersonApiService) ShowPerson(ctx context.Context) (openapi.ImplResponse, error) {
// TODO: Add your own implementation of the ShowPerson method here.
// For example, you could retrieve a person's details and return them as follows:
person := openapi.Person{Id: 23, Name: "Vark Thins", Age: 20}
return openapi.Response(http.StatusOK, person), nil
}
func main() {
log.Printf("Server started")
PersonApiService := NewMyPersonApiService()
PersonApiController := openapi.NewPersonApiController(PersonApiService)
router := openapi.NewRouter(PersonApiController)
log.Fatal(http.ListenAndServe(":8080", router))
}