fix #59: prevent caching of github contribution calendar

Author: kamilsk

go.mod

@@ -18,6 +18,7 @@ require (
 	go.octolab.org v0.12.0
 	go.octolab.org/toolkit/cli v0.6.3
 	go.octolab.org/toolkit/config v0.0.4
+	go.octolab.org/toolkit/protocol v0.1.0
 	golang.org/x/oauth2 v0.0.0-20220524215830-622c5d57e401
 	golang.org/x/sync v0.0.0-20220513210516-0976fa681c29
 	gopkg.in/yaml.v2 v2.4.0

go.sum

@@ -10,6 +10,7 @@ import (
 
 	"github.com/PuerkitoBio/goquery"
 	"go.octolab.org/safe"
+	"go.octolab.org/toolkit/protocol/http/header"
 	"go.octolab.org/unsafe"
 	"golang.org/x/sync/errgroup"
 
@@ -78,6 +79,7 @@ func fetchContributions(ctx context.Context, user string, year int) (*goquery.Do
 		HttpOnly: true,
 		SameSite: http.SameSiteLaxMode,
 	})
+	req.Header.Set(header.CacheControl, "no-cache")
 
 	// TODO:debt use srv.client.Client() instead
 	resp, err := http.DefaultClient.Do(req)