云函数使用switch（）函数报错

exports.main = async (event, context) => {
  const wxContext = cloud.getWXContext()
  switch (req_type) {
    case 'Add': {
      return await db.collection('RepairOrder').add({
        data: {
          date: event.date,
          time: event.time,
          communityId: event.communityId,
          orderType: event.orderType,
          orderProgress: event.orderProgress,
          projectName: event.projectName,
          projectType: event.projectType,
          projectPrice: event.projectPrice,
          descValue: event.descValue,
          address: event.address,
          contactInfo: event.contactInfo,
          status: event.status,
          userId: wxContext.OPENID,
          userInfo: event.userInfo,
          createAt: new Date()
        }
      }).then( res => {
        console.log(res)
        return res
      })
    }
    case 'Recall' : {
      return await db.collection('RepairOrder').where({
        _id: event._id
      })
      .update({
        data: {
          status: event.status,
          deleteAt: new Date()
        }
      }).then( res => {
        console.log(res)
        return res
      })
    }
    case 'Repairman' : {
      return await db.collection('RepairOrder').where({
        _id: event._id
      })
      .update({
        data: {
          orderProgress: _.push(event.progressItem),
        }
      }).then( res => {
        console.log(res)
        return res
      })
    }
    default: {
      return
    }
  }

js文件

wx.cloud.callFunction({
      name: 'add_RepairOrder',
      data: {
        req_type: 'Add',
        date: this.data.date,
        time: this.data.time,
        communityId: this.data.communityId,
        orderType: this.data.orderType,
        orderProgress: this.data.orderProgress,
        projectName: this.data.projectName,
        projectType: this.data.projectType,
        projectPrice: this.data.projectPrice,
        descValue: this.data.descValue,
        address: this.data.address,
        contactInfo: this.data.contactInfo,
        status: this.data.status,
        userInfo: app.globalData.userInfo
      }
    }).then( res => {
      console.log(res)
      // 强制刷新上一页
      var pages = getCurrentPages();             //  获取页面栈
      var prevPage = pages[pages.length - 2];    // 上一个页面
      prevPage.setData({
        update: true
      })
      wx.hideLoading()
      wx.navigateBack({
        delta: 1
      })
    })