Fix race in tests.

export_test.go

@@ -2,6 +2,7 @@ package redis
 
 import (
 	"net"
+	"sync"
 	"time"
 )
 
@@ -19,12 +20,18 @@ func (cn *conn) SetNetConn(netcn net.Conn) {
 	cn.netcn = netcn
 }
 
+var timeMu sync.Mutex
+
 func SetTime(tm time.Time) {
+	timeMu.Lock()
 	now = func() time.Time {
 		return tm
 	}
+	timeMu.Unlock()
 }
 
 func RestoreTime() {
+	timeMu.Lock()
 	now = time.Now
+	timeMu.Unlock()
 }