DialHost must connect to the requested host

When a hostname resolves to multiple hosts, multiple HostInfos are
generated. DialHost must connect to the host received as parameter.
If the hostname is used to establish the connection, the dns could
resolve to another host.
The hostname should still be used to verify the TLS connection.

Author: laurovenancio

dial.go

@@ -45,11 +45,12 @@ func (hd *defaultHostDialer) DialHost(ctx context.Context, host *HostInfo) (*Dia
 		return nil, fmt.Errorf("host missing port: %v", port)
 	}
 
-	addr := host.HostnameAndPort()
-	conn, err := hd.dialer.DialContext(ctx, "tcp", addr)
+	connAddr := host.ConnectAddressAndPort()
+	conn, err := hd.dialer.DialContext(ctx, "tcp", connAddr)
 	if err != nil {
 		return nil, err
 	}
+	addr := host.HostnameAndPort()
 	return WrapTLS(ctx, conn, addr, hd.tlsConfig)
 }
 

host_source.go

@@ -401,6 +401,13 @@ func (h *HostInfo) HostnameAndPort() string {
 	return net.JoinHostPort(h.hostname, strconv.Itoa(h.port))
 }
 
+func (h *HostInfo) ConnectAddressAndPort() string {
+        h.mu.Lock()
+        defer h.mu.Unlock()
+        addr, _ := h.connectAddressLocked()
+        return net.JoinHostPort(addr.String(), strconv.Itoa(h.port))
+}
+
 func (h *HostInfo) String() string {
 	h.mu.RLock()
 	defer h.mu.RUnlock()