Use method as cache key prefix for non-GET requests

httpcache.go

@@ -41,7 +41,11 @@ type Cache interface {
 
 // cacheKey returns the cache key for req.
 func cacheKey(req *http.Request) string {
-	return req.URL.String()
+	if req.Method == http.MethodGet {
+		return req.URL.String()
+	} else {
+		return req.Method + " " + req.URL.String()
+	}
 }
 
 // CachedResponse returns the cached http.Response for req if present, and nil

httpcache_test.go

@@ -218,6 +218,30 @@ func TestCacheableMethod(t *testing.T) {
 	}
 }
 
+func TestDontServeHeadResponseToGetRequest(t *testing.T) {
+	resetTest()
+	url := s.server.URL + "/"
+	req, err := http.NewRequest(http.MethodHead, url, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = s.client.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	req, err = http.NewRequest(http.MethodGet, url, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp, err := s.client.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if resp.Header.Get(XFromCache) != "" {
+		t.Errorf("Cache should not match")
+	}
+}
+
 func TestDontStorePartialRangeInCache(t *testing.T) {
 	resetTest()
 	{