[skip ci] Add comment for grpcclient.ClientBase (#12966)

Signed-off-by: shaoyue.chen <shaoyue.chen@zilliz.com>

internal/util/grpcclient/client.go

@@ -33,6 +33,7 @@ type GrpcClient interface {
 	Close() error
 }
 
+// ClientBase is a base of grpc client
 type ClientBase struct {
 	getAddrFunc   func() (string, error)
 	newGrpcClient func(cc *grpc.ClientConn) interface{}
@@ -45,10 +46,12 @@ type ClientBase struct {
 	ClientMaxRecvSize int
 }
 
+// SetRole sets role of client
 func (c *ClientBase) SetRole(role string) {
 	c.role = role
 }
 
+// GetRole returns role of client
 func (c *ClientBase) GetRole() string {
 	return c.role
 }