Use net.JoinHostPort and net.SplitHostPort for IPv6-safe host:port handling (#5836)

client/internal/relay/relay.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"net"
+	"strconv"
 	"sync"
 	"time"
 
@@ -257,7 +258,7 @@ func (p *StunTurnProbe) probeTURN(ctx context.Context, uri *stun.URI) (addr stri
 		}
 	}()
 
-	turnServerAddr := fmt.Sprintf("%s:%d", uri.Host, uri.Port)
+	turnServerAddr := net.JoinHostPort(uri.Host, strconv.Itoa(uri.Port))
 
 	var conn net.PacketConn
 	switch uri.Proto {