Remove pessimistic String calls for low level logs (#687)

agent.go

@@ -728,7 +728,7 @@ func (a *Agent) addCandidate(ctx context.Context, c Candidate, candidateConn net
 		set := a.localCandidates[c.NetworkType()]
 		for _, candidate := range set {
 			if candidate.Equal(c) {
-				a.log.Debugf("Ignore duplicate candidate: %s", c.String())
+				a.log.Debugf("Ignore duplicate candidate: %s", c)
 				if err := c.close(); err != nil {
 					a.log.Warnf("Failed to close duplicate candidate: %v", err)
 				}
@@ -886,7 +886,7 @@ func (a *Agent) findRemoteCandidate(networkType NetworkType, addr net.Addr) Cand
 }
 
 func (a *Agent) sendBindingRequest(m *stun.Message, local, remote Candidate) {
-	a.log.Tracef("Ping STUN from %s to %s", local.String(), remote.String())
+	a.log.Tracef("Ping STUN from %s to %s", local, remote)
 
 	a.invalidatePendingBindingRequests(time.Now())
 	a.pendingBindingRequests = append(a.pendingBindingRequests, bindingRequest{
@@ -1001,7 +1001,7 @@ func (a *Agent) handleInbound(m *stun.Message, local Candidate, remote net.Addr)
 
 		a.selector.HandleSuccessResponse(m, local, remoteCandidate, remote)
 	} else if m.Type.Class == stun.ClassRequest {
-		a.log.Tracef("Inbound STUN (Request) from %s to %s, useCandidate: %v", remote.String(), local.String(), m.Contains(stun.AttrUseCandidate))
+		a.log.Tracef("Inbound STUN (Request) from %s to %s, useCandidate: %v", remote, local, m.Contains(stun.AttrUseCandidate))
 
 		if err = stunx.AssertUsername(m, a.localUfrag+":"+a.remoteUfrag); err != nil {
 			a.log.Warnf("Discard message from (%s), %v", remote, err)