Timeout well-known requests (#438)

fclient/well_known.go

@@ -38,12 +38,13 @@ func LookupWellKnown(ctx context.Context, serverNameType spec.ServerName) (*Well
 	wellKnownPath := "/.well-known/matrix/server"
 
 	// Request server's well-known record
-
 	req, err := http.NewRequestWithContext(ctx, "GET", "https://"+serverName+wellKnownPath, nil)
 	if err != nil {
 		return nil, err
 	}
-	resp, err := http.DefaultClient.Do(req)
+	// Given well-known should be quite small and fast to fetch, timeout the request after 30s.
+	client := http.Client{Timeout: time.Second * 30}
+	resp, err := client.Do(req)
 	if err != nil {
 		return nil, err
 	}