go并发的问题

package main import ( "yangsheng/models" //"fmt" "runtime" //"time" //"os" ) func getinfo(id int,url string,a,b chan bool) { a<-true isok:=false defer func() { b <-isok }() info:=models.GetInfo(url) if len(info["Title"]) > 0 { var inmodel models.Info var durls models.Deurls inmodel.Url = info["Url"] if inmodel.Read("title") !=nil { inmodel.Title = info["Title"] inmodel.Content = info["Content"] _,err :=inmodel.Insert() if err == nil { durls.Id = id durls.Status = 1 durls.Update("Status") } else { } } } else { } isok=true } func main() { NCPU := runtime.NumCPU() runtime.GOMAXPROCS(NCPU) models.Init() details :=new(models.Deurls) var list []*models.Deurls a :=make(chan bool,10) b :=make(chan bool,1) for i:=0;i<10;i++ { details.Query().OrderBy("-id").Limit(i*2000,2000).All(&list) for _,v := range list { go getinfo(v.Id,v.Url,a,b) } } for j:=0;j<20000;j++ { <-b <-a } close(a) close(b) } 我这段代码，是用来采集数据的。总共有2万条数据。运行一会，他就提示以下错误。