Use time.NewTimer() instead of time.After()

For efficiency, cancel time.Timer after no longer needed.
See https://pkg.go.dev/time#After

Author: afriza

api/client.go

@@ -68,9 +68,13 @@ func (c *Client) SendRequest(requestBody Params, responseBody interface{}) error
 	}
 
 	var response *opcodes.RequestResponse
+	timeout, timer := newTimeoutTimer(c.ResponseTimeout * time.Millisecond)
 	select {
 	case response = <-c.IncomingResponses:
-	case <-time.After(c.ResponseTimeout * time.Millisecond):
+		if timer != nil {
+			timer.Stop()
+		}
+	case <-timeout:
 		return fmt.Errorf("request %s: timeout waiting for response from server", name)
 	}
 
@@ -123,3 +127,15 @@ func (c *Client) SendRequest(requestBody Params, responseBody interface{}) error
 
 	return nil
 }
+
+// newTimeoutTimer is an alternative to time.After with the possibility to cancel
+// the underlying time.Timer to achieve better efficiency.
+// time.Duration d <= 0 means no timeout or waiting forever.
+// See https://pkg.go.dev/time#After
+func newTimeoutTimer(d time.Duration) (timeout <-chan time.Time, timer *time.Timer) {
+	if d > 0 {
+		timer = time.NewTimer(d)
+		timeout = timer.C
+	}
+	return
+}

client.go

@@ -172,10 +172,14 @@ func (c *Client) connect() (err error) {
 	go c.handleRawServerMessages(authComplete)
 	go c.handleOpcodes(authComplete)
 
+	timeout, timer := newTimeoutTimer(c.ResponseTimeout * time.Millisecond)
 	select {
 	case a := <-authComplete:
+		if timer != nil {
+			timer.Stop()
+		}
 		return a
-	case <-time.After(c.ResponseTimeout * time.Millisecond):
+	case <-timeout:
 		return fmt.Errorf("timeout waiting for authentication: %dms", c.ResponseTimeout)
 	}
 }
@@ -355,7 +359,7 @@ func (c *Client) writeEvent(event interface{}) {
 			// incoming events was full (but might not be by now),
 			// so safely read off the oldest, and write the latest
 			select {
-			case _ = <-c.IncomingEvents:
+			case <-c.IncomingEvents:
 			default:
 			}
 
@@ -369,3 +373,15 @@ func (c *Client) Listen(f func(interface{})) {
 		f(event)
 	}
 }
+
+// newTimeoutTimer is an alternative to time.After with the possibility to cancel
+// the underlying time.Timer to achieve better efficiency.
+// time.Duration d <= 0 means no timeout or waiting forever.
+// See https://pkg.go.dev/time#After
+func newTimeoutTimer(d time.Duration) (timeout <-chan time.Time, timer *time.Timer) {
+	if d > 0 {
+		timer = time.NewTimer(d)
+		timeout = timer.C
+	}
+	return
+}