以下三种实现之间是否存在差异(在性能方面)？:mustGetSpeed:=func()string{...returnspeed}for_,item:=rangeitems{speed,err:=strconv.Atoi(mustGetSpeed())...}for_,item:=rangeitems{mustGetSpeed:=func()string{...returnspeed}speed,err:=strconv.Atoi(mustGetSpeed())...}for_,item:=rangeitems{speed,err:=strconv.Atoi(func()string{

以下三种实现之间是否存在差异(在性能方面)？:mustGetSpeed:=func()string{...returnspeed}for_,item:=rangeitems{speed,err:=strconv.Atoi(mustGetSpeed())...}for_,item:=rangeitems{mustGetSpeed:=func()string{...returnspeed}speed,err:=strconv.Atoi(mustGetSpeed())...}for_,item:=rangeitems{speed,err:=strconv.Atoi(func()string{