fix golint issues in core/syncx (#526)

core/syncx/atomicduration.go

@@ -5,26 +5,32 @@ import (
 	"time"
 )
 
+// An AtomicDuration is an implementation of atomic duration.
 type AtomicDuration int64
 
+// NewAtomicDuration returns an AtomicDuration.
 func NewAtomicDuration() *AtomicDuration {
 	return new(AtomicDuration)
 }
 
+// ForAtomicDuration returns an AtomicDuration with given value.
 func ForAtomicDuration(val time.Duration) *AtomicDuration {
 	d := NewAtomicDuration()
 	d.Set(val)
 	return d
 }
 
+// CompareAndSwap compares current value with old, if equals, set the value to val.
 func (d *AtomicDuration) CompareAndSwap(old, val time.Duration) bool {
 	return atomic.CompareAndSwapInt64((*int64)(d), int64(old), int64(val))
 }
 
+// Load loads the current duration.
 func (d *AtomicDuration) Load() time.Duration {
 	return time.Duration(atomic.LoadInt64((*int64)(d)))
 }
 
+// Set sets the value to val.
 func (d *AtomicDuration) Set(val time.Duration) {
 	atomic.StoreInt64((*int64)(d), int64(val))
 }