方案詳解：使用laravel解決庫存超出問題

    /**      * 錯誤示范      * Create by Peter Yang      * 2021-06-08 10:57:59      * @return string      */     function test1()     {          //商品id         $id = request()->input('id');          $product = Product::where('id', $id)->firstOrFail();          if ($product->num <= 0) {              return "賣光啦！！";         }          //倉庫減1         $product->decrement('num');          return "success";      }

package mainimport (     "fmt"     "github.com/PeterYangs/tools/http"     "sync")func main() {      client := http.Client()      wait := sync.WaitGroup{}      for i := 0; i < 50; i++ {          wait.Add(1)          go func(w *sync.WaitGroup) {              defer wait.Done()              res, _ := client.Request().GetToString("http://www.api/test1?id=1")              fmt.Println(res)          }(&wait)      }      wait.Wait()}

    /**      * redis原子鎖      * Create by Peter Yang      * 2021-06-08 11:00:31      */     function test2()     {         //商品id         $id = request()->input('id');          $lock = Cache::lock("product_" . $id, 10);          try {              //最多等待5秒，5秒后未獲取到鎖，則拋出異常             $lock->block(5);              $product = Product::where('id', $id)->firstOrFail();              if ($product->num <= 0) {                  return "賣光啦！！";             }             //倉庫減1             $product->decrement('num');              return 'success';          }catch (LockTimeoutException $e) {              return '當前人數過多';          } finally {              optional($lock)->release();         }     }

    /**      * mysql悲觀鎖      * Create by Peter Yang      * 2021-06-08 11:00:47      */     function test3()     {          //商品id         $id = request()->input('id');          try {             DB::beginTransaction();             $product = Product::where('id', $id)->lockForUpdate()->first();              if ($product->num <= 0) {                  return "賣光啦！！";             }              //倉庫減1             $product->decrement('num');              DB::commit();              return "success";          } catch (Exception $exception) {          }      }

    /**      * mysql樂觀鎖      * Create by Peter Yang      * 2021-06-08 11:00:47      */     function test4()     {          //商品id         $id = request()->input('id');          $product = Product::where('id', $id)->first();          if ($product->num <= 0) {              return "賣光啦！！";         }          //修改前檢查庫存和之前是否一致，不一致說明已經有變動，則放棄更改         $res = DB::update('UPDATE `product` SET num = num -1 WHERE id = ? AND num=?', [$id, $product->num]);          if (!$res) {              return '當前人數過多';          }          return 'success';       }

DB::update('UPDATE `product` SET num = num -1 WHERE id = ? AND num-1 >= 0', [$id]);