net: add DialUDPContext version of DialUDP

Fixes #49097

Author: moredure

src/net/udpsock.go

@@ -284,6 +284,23 @@ func newUDPConn(fd *netFD) *UDPConn { return &UDPConn{conn{fd}} }
 // If the IP field of raddr is nil or an unspecified IP address, the
 // local system is assumed.
 func DialUDP(network string, laddr, raddr *UDPAddr) (*UDPConn, error) {
+	return DialUDPContext(context.Background(), network, laddr, raddr)
+}
+
+// DialUDPContext acts like DialUDP but connects using
+// the provided context.
+//
+// The provided Context must be non-nil.
+//
+// The network must be a UDP network name; see func Dial for details.
+//
+// If laddr is nil, a local address is automatically chosen.
+// If the IP field of raddr is nil or an unspecified IP address, the
+// local system is assumed.
+func DialUDPContext(ctx context.Context, network string, laddr, raddr *UDPAddr) (*UDPConn, error) {
+	if ctx == nil {
+		panic("nil context")
+	}
 	switch network {
 	case "udp", "udp4", "udp6":
 	default:
@@ -293,7 +310,7 @@ func DialUDP(network string, laddr, raddr *UDPAddr) (*UDPConn, error) {
 		return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: nil, Err: errMissingAddress}
 	}
 	sd := &sysDialer{network: network, address: raddr.String()}
-	c, err := sd.dialUDP(context.Background(), laddr, raddr)
+	c, err := sd.dialUDP(ctx, laddr, raddr)
 	if err != nil {
 		return nil, &OpError{Op: "dial", Net: network, Source: laddr.opAddr(), Addr: raddr.opAddr(), Err: err}
 	}