fix golint issues in core/syncx (#526)

core/syncx/cond.go

@@ -7,17 +7,19 @@ import (
 	"github.com/tal-tech/go-zero/core/timex"
 )
 
+// A Cond is used to wait for conditions.
 type Cond struct {
 	signal chan lang.PlaceholderType
 }
 
+// NewCond returns a Cond.
 func NewCond() *Cond {
 	return &Cond{
 		signal: make(chan lang.PlaceholderType),
 	}
 }
 
-// WaitWithTimeout wait for signal return remain wait time or timed out
+// WaitWithTimeout wait for signal return remain wait time or timed out.
 func (cond *Cond) WaitWithTimeout(timeout time.Duration) (time.Duration, bool) {
 	timer := time.NewTimer(timeout)
 	defer timer.Stop()
@@ -33,7 +35,7 @@ func (cond *Cond) WaitWithTimeout(timeout time.Duration) (time.Duration, bool) {
 	}
 }
 
-// Wait for signal
+// Wait waits for signals.
 func (cond *Cond) Wait() {
 	<-cond.signal
 }