client: set the client timout on the dialer, close connection on err

Client.Timout isn't respected for the dial. Requests will hang on dial
until OS-level timouts kick in unless there is a Request.Context with
a deadline. We also fail to close the connection on errors.

This change sets the client timeout as the dialer timeout so that it
will be respected. It also ensures that we close the connection if we
fail to make the request.

client.go

@@ -68,24 +68,49 @@ func (c *Client) Do(req *Request) (*Response, error) {
 	if ctx == nil {
 		ctx = context.Background()
 	}
-	netConn, err := (&net.Dialer{}).DialContext(ctx, "tcp", req.Host)
+
+	start := time.Now()
+	dialer := net.Dialer{
+		Timeout: c.Timeout,
+	}
+
+	netConn, err := dialer.DialContext(ctx, "tcp", req.Host)
 	if err != nil {
 		return nil, err
 	}
+
 	conn := tls.Client(netConn, config)
+
 	// Set connection deadline
 	if c.Timeout != 0 {
-		err := conn.SetDeadline(time.Now().Add(c.Timeout))
+		err := conn.SetDeadline(start.Add(c.Timeout))
 		if err != nil {
 			return nil, fmt.Errorf(
 				"failed to set connection deadline: %w", err)
 		}
 	}
 
+	resp, err := c.do(conn, req)
+	if err != nil {
+		// If we fail to perform the request/response we have
+		// to take responsibility for closing the connection.
+		_ = conn.Close()
+
+		return nil, err
+	}
+
+	// Store connection state
+	resp.TLS = conn.ConnectionState()
+
+	return resp, nil
+}
+
+func (c *Client) do(conn *tls.Conn, req *Request) (*Response, error) {
+
 	// Write the request
 	w := bufio.NewWriter(conn)
 
-	err = req.Write(w)
+	err := req.Write(w)
 	if err != nil {
 		return nil, fmt.Errorf(
 			"failed to write request data: %w", err)
@@ -100,8 +125,6 @@ func (c *Client) Do(req *Request) (*Response, error) {
 	if err != nil {
 		return nil, err
 	}
-	// Store connection state
-	resp.TLS = conn.ConnectionState()
 
 	return resp, nil
 }