feat: optimized-error-handling&remove unused constant

openplatform/context/accessToken.go

@@ -100,11 +100,8 @@ func (ctx *Context) GetPreCodeContext(stdCtx context.Context) (string, error) {
 	var ret struct {
 		PreCode string `json:"pre_auth_code"`
 	}
-	if err := json.Unmarshal(body, &ret); err != nil {
-		return "", err
-	}
-
-	return ret.PreCode, nil
+	err = json.Unmarshal(body, &ret)
+	return ret.PreCode, err
 }
 
 // GetPreCode 获取预授权码