Improve candidate base locking mechanism

Use atomic values for lastReceived and lastSenti. The lock around
resolvedAddr and conn was not being used, so I removed it

candidate_base.go

@@ -3,7 +3,7 @@ package ice
 import (
 	"fmt"
 	"net"
-	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/pion/logging"
@@ -22,12 +22,11 @@ type candidateBase struct {
 
 	resolvedAddr *net.UDPAddr
 
-	lock         sync.RWMutex
-	lastSent     time.Time
-	lastReceived time.Time
+	lastSent     atomic.Value
+	lastReceived atomic.Value
+	conn         net.PacketConn
 
 	currAgent *Agent
-	conn      net.PacketConn
 	closeCh   chan struct{}
 	closedCh  chan struct{}
 }
@@ -140,8 +139,6 @@ func handleInboundCandidateMsg(c Candidate, buffer []byte, srcAddr net.Addr, log
 
 // close stops the recvLoop
 func (c *candidateBase) close() error {
-	c.lock.Lock()
-	defer c.lock.Unlock()
 	if c.conn != nil {
 		// Unblock recvLoop
 		close(c.closeCh)
@@ -197,29 +194,21 @@ func (c *candidateBase) String() string {
 // LastReceived returns a time.Time indicating the last time
 // this candidate was received
 func (c *candidateBase) LastReceived() time.Time {
-	c.lock.RLock()
-	defer c.lock.RUnlock()
-	return c.lastReceived
+	return c.lastReceived.Load().(time.Time)
 }
 
 func (c *candidateBase) setLastReceived(t time.Time) {
-	c.lock.Lock()
-	defer c.lock.Unlock()
-	c.lastReceived = t
+	c.lastReceived.Store(t)
 }
 
 // LastSent returns a time.Time indicating the last time
 // this candidate was sent
 func (c *candidateBase) LastSent() time.Time {
-	c.lock.RLock()
-	defer c.lock.RUnlock()
-	return c.lastSent
+	return c.lastSent.Load().(time.Time)
 }
 
 func (c *candidateBase) setLastSent(t time.Time) {
-	c.lock.Lock()
-	defer c.lock.Unlock()
-	c.lastSent = t
+	c.lastSent.Store(t)
 }
 
 func (c *candidateBase) seen(outbound bool) {
@@ -231,8 +220,6 @@ func (c *candidateBase) seen(outbound bool) {
 }
 
 func (c *candidateBase) addr() *net.UDPAddr {
-	c.lock.Lock()
-	defer c.lock.Unlock()
 	return c.resolvedAddr
 }