server: fix a goroutine leak in unit test (#6183)
server: fix a goroutine leak in unit test (#6183)


CodeRushing/tidb,c4pt0r/tidb,EvilMcJerkface/tidb,mccxj/tidb,pingcap/tidb,coocood/tidb,c4pt0r/tidb,pingcap/tidb,kyle-wang/tidb,XuHuaiyu/tidb,ngaut/tidb,Cofyc/tidb,ming-relax/tidb,Nify/tidb,c4pt0r/tidb,c4pt0r/tidb,qiuyesuifeng/tidb,ngaut/tidb,ngaut/tidb,wusphinx/tidb,coocood/tidb,XuHuaiyu/tidb,pingcap/tidb,pingcap/tidb,kyle-wang/tidb,c4pt0r/tidb,kyle-wang/tidb,cosmtrek/tidb,pingcap/tidb,ngaut/tidb,kyle-wang/tidb,qiuyesuifeng/tidb,ngaut/tidb,mccxj/tidb,c4pt0r/tidb,EvilMcJerkface/tidb,Cofyc/tidb,ngaut/tidb,kyle-wang/tidb,wusphinx/tidb,cosmtrek/tidb,ming-relax/tidb,CodeRushing/tidb,Nify/tidb,kyle-wang/tidb,pingcap/tidb,tiancaiamao/tidb,tiancaiamao/tidb