add negative duration fix for tcp proxydial and also fix documentation

dialoptions.go

@@ -414,7 +414,7 @@ func WithTimeout(d time.Duration) DialOption {
 // returned by f, gRPC checks the error's Temporary() method to decide if it
 // should try to reconnect to the network address.
 //
-// Note: As of Go 1.13, the standard library overrides the OS defaults for
+// Note: As of Go 1.21, the standard library overrides the OS defaults for
 // TCP keepalive time and interval to 15s.
 // To retain OS defaults, use a net.Dialer with the KeepAlive field set to a
 // negative value.

internal/transport/proxy.go

@@ -28,6 +28,7 @@ import (
 	"net/http"
 	"net/http/httputil"
 	"net/url"
+	"time"
 )
 
 const proxyAuthHeaderKey = "Proxy-Authorization"
@@ -122,7 +123,7 @@ func proxyDial(ctx context.Context, addr string, grpcUA string) (conn net.Conn,
 		newAddr = proxyURL.Host
 	}
 
-	conn, err = (&net.Dialer{}).DialContext(ctx, "tcp", newAddr)
+	conn, err = (&net.Dialer{KeepAlive: time.Duration(-1)}).DialContext(ctx, "tcp", newAddr)
 	if err != nil {
 		return
 	}

server.go

@@ -814,7 +814,7 @@ func (l *listenSocket) Close() error {
 // this method returns.
 // Serve will return a non-nil error unless Stop or GracefulStop is called.
 //
-// Note: As of Go 1.13, the standard library overrides the OS defaults for
+// Note: As of Go 1.21, the standard library overrides the OS defaults for
 // TCP keepalive time and interval to 15s.
 // To retain OS defaults, pass a net.Listener created by calling the Listen method
 // on a net.ListenConfig with the `KeepAlive` field set to a negative value.