Add DoWithCustomClient function

Author: Pedro De Brito

request.go

@@ -114,6 +114,37 @@ func DoWithStringResponse(params Params) (result string, returnErr error) {
 	return string(bodyBytes), nil
 }
 
+// DoWithCustomClient is the same as Do but will make the request using the
+// supplied http.Client instead of the cachedClient.
+func DoWithCustomClient(params Params, responseBody interface{}, client *http.Client) (returnErr error) {
+	req, err := createRequest(params)
+	if err != nil {
+		return fmt.Errorf("failed to create request: %w", err)
+	}
+
+	res, err := client.Do(req)
+	if err != nil {
+		return fmt.Errorf("failed to send request: %w", err)
+	}
+
+	defer func() {
+		if cErr := res.Body.Close(); cErr != nil && returnErr == nil {
+			returnErr = cErr
+		}
+	}()
+
+	err = checkResponseCode(res, params.ExpectedResponseCode)
+	if err != nil {
+		return err
+	}
+
+	if responseBody == nil {
+		return nil
+	}
+
+	return json.NewDecoder(res.Body).Decode(responseBody)
+}
+
 func createRequest(params Params) (*http.Request, error) {
 	reader, err := convertToReader(params.Body)
 	if err != nil {

request_test.go

@@ -4,13 +4,16 @@ import (
 	"fmt"
 	"io/ioutil"
 	"net/http"
+	"net/http/cookiejar"
 	"net/http/httptest"
+	"net/url"
 	"strings"
 	"testing"
 	"time"
 
 	"github.com/fastbill/go-httperrors/v2"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 type Input struct {
@@ -318,6 +321,29 @@ func TestDoWithStringResponse(t *testing.T) {
 	})
 }
 
+func TestDoWithCustomClient(t *testing.T) {
+	customClient := GetClient()
+
+	jar, err := cookiejar.New(nil)
+	require.NoError(t, err)
+	customClient.Jar = jar
+
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Set-Cookie", "foo=bar")
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	u, err := url.Parse(ts.URL)
+	require.NoError(t, err)
+	params := Params{
+		URL: u.String(),
+	}
+	err = DoWithCustomClient(params, nil, customClient)
+	require.NoError(t, err)
+
+	require.Equal(t, "foo=bar", jar.Cookies(u)[0].String())
+}
+
 func TestGet(t *testing.T) {
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		assert.Equal(t, r.Method, http.MethodGet)