move building of homeservers array into separate function

Move building of homeservers array into separate function to make Get
function easier to follow.

roominfotree/roominfotree.go

@@ -74,6 +74,23 @@ func getMembersByHomeserverByRoomID(roomIDs []id.RoomID, client *mautrix.Client)
 	return membersByHomeserverByRoomID
 }
 
+// Gets the homeservers appearing in the given membersByHomeserverByRoomID map tree.
+func getHomeservers(membersByHomeserverByRoomID map[id.RoomID]map[string]uint) []string {
+	homeserverSet := make(map[string]bool)
+	for _, membersByHomeserver := range membersByHomeserverByRoomID {
+		for hs := range membersByHomeserver {
+			homeserverSet[hs] = true
+		}
+	}
+
+	homeservers := make([]string, 0, len(homeserverSet))
+	for hs := range homeserverSet {
+		homeservers = append(homeservers, hs)
+	}
+
+	return homeservers
+}
+
 func getServerVersionInfoByHomeserver(homeservers []string, federationClient *fclient.Client) map[string](fclient.Version) {
 	homeserverChannel := make(chan string)
 	go func() {
@@ -114,18 +131,7 @@ func getServerVersionInfoByHomeserver(homeservers []string, federationClient *fc
 
 func Get(roomIDs []id.RoomID, client *mautrix.Client, federationClient *fclient.Client) RoomInfoTree {
 	membersByHomeserverByRoomID := getMembersByHomeserverByRoomID(roomIDs, client)
-
+	homeservers := getHomeservers(membersByHomeserverByRoomID)
-	homeserverSet := make(map[string]bool)
-	for _, membersByHomeserver := range membersByHomeserverByRoomID {
-		for hs := range membersByHomeserver {
-			homeserverSet[hs] = true
-		}
-	}
-	homeservers := make([]string, 0, len(homeserverSet))
-	for hs := range homeserverSet {
-		homeservers = append(homeservers, hs)
-	}
-
 	serverVersionInfoByHomeserver := getServerVersionInfoByHomeserver(homeservers, federationClient)
 
 	roomInfoTree := make(RoomInfoTree)