feat: auto calculate pagination in fetcher

also refactor a little the worker pool

examples/usage.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	"database/sql"
 	"encoding/json"
 	"fmt"
@@ -16,7 +17,7 @@ import (
 )
 
 type PokeApiListResponse[T any] struct {
-	Count    int    `json:"count"`
+	Count    uint64 `json:"count"`
 	Next     string `json:"next"`
 	Previous string `json:"previous"`
 	Results  []T    `json:"results"`
@@ -42,17 +43,22 @@ type Pokemon struct {
 }
 
 func getPokedexs(
+	ctx context.Context,
 	pagination synchronizator.Pagination,
-) ([]*synchronizator.Collection, synchronizator.Pagination, error) {
+) (synchronizator.FetchCollectionResponse, error) {
+	payload := synchronizator.FetchCollectionResponse{
+		Pagination: pagination,
+	}
+
 	var collections []*synchronizator.Collection
 
 	params := url.Values{}
-	params.Add("offset", strconv.Itoa(pagination.Offset))
-	params.Add("limit", strconv.Itoa(pagination.Limit))
+	params.Add("offset", strconv.FormatUint(pagination.Offset, 10))
+	params.Add("limit", strconv.FormatUint(pagination.Limit, 10))
 
 	resp, err := http.Get("https://pokeapi.co/api/v2/pokedex?" + params.Encode())
 	if err != nil {
-		return nil, pagination, err
+		return payload, err
 	}
 
 	body, err := io.ReadAll(resp.Body)
@@ -61,7 +67,7 @@ func getPokedexs(
 	var data PokeApiListResponse[Pokedex]
 	err = json.Unmarshal(body, &data)
 	if err != nil {
-		return nil, pagination, err
+		return payload, err
 	}
 
 	collections = make([]*synchronizator.Collection, 0, len(data.Results))
@@ -71,18 +77,20 @@ func getPokedexs(
 		metadata, err := json.Marshal(pokedex)
 		collection := synchronizator.NewCollection(collection_name, metadata)
 		if err != nil {
-			return nil, pagination, err
+			return payload, err
 		}
 		collections = append(collections, collection)
 	}
 
 	// fmt.Println(data)
 
-	pagination.Offset += pagination.Limit
-	pagination.HasMore = data.Next != ""
-	pagination.Total = data.Count
+	payload.Offset += pagination.Limit
+	payload.HasMore = data.Next != ""
+	payload.Total = data.Count
 
-	return collections, pagination, nil
+	payload.Response = collections
+
+	return payload, nil
 }
 
 func getPokemons(
@@ -158,7 +166,9 @@ func main() {
 		return
 	}
 
-	err = pokeApi.FetchCollections(getPokedexs, synchronizator.StartPagination)
+	pagination := synchronizator.StartPagination
+
+	err = pokeApi.FetchCollections(getPokedexs, pagination)
 	if err != nil {
 		fmt.Println(err)
 		return