mess about with some structure to help w/ deref

internal/transport/derefmedia.go

@@ -0,0 +1,42 @@
+package transport
+
+import (
+	"context"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+)
+
+func (t *transport) DereferenceMedia(c context.Context, iri *url.URL, expectedContentType string) ([]byte, error) {
+	l := t.log.WithField("func", "DereferenceMedia")
+	l.Debugf("performing GET to %s", iri.String())
+	req, err := http.NewRequest("GET", iri.String(), nil)
+	if err != nil {
+		return nil, err
+	}
+	req = req.WithContext(c)
+	if expectedContentType == "" {
+		req.Header.Add("Accept", "*/*")
+	} else {
+		req.Header.Add("Accept", expectedContentType)
+	}
+	req.Header.Add("Date", t.clock.Now().UTC().Format("Mon, 02 Jan 2006 15:04:05")+" GMT")
+	req.Header.Add("User-Agent", fmt.Sprintf("%s %s", t.appAgent, t.gofedAgent))
+	req.Header.Set("Host", iri.Host)
+	t.getSignerMu.Lock()
+	err = t.getSigner.SignRequest(t.privkey, t.pubKeyID, req, nil)
+	t.getSignerMu.Unlock()
+	if err != nil {
+		return nil, err
+	}
+	resp, err := t.client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("GET request to %s failed (%d): %s", iri.String(), resp.StatusCode, resp.Status)
+	}
+	return ioutil.ReadAll(resp.Body)
+}