求助大佬，使用tedious模块连接SQLserver数据库遇到的问题。

第一次访问没有问题，第二次访问会卡在执行SQL的地方。代码如下： tedious.js const Connection = require(‘tedious’).Connection;
const Request = require(‘tedious’).Request;

exports.mssql = function(config){
this.connection = new Connection(config);

this.query = function(str,callback){          //执行查询    
    var connection = this.connection;    
    var rows={};    
    connection.on('connect', function(err){                 //连接数据库，执行匿名函数    
        if(err){    
            callback({'err':err['message']+'请检查账号、密码是否正确,且数据库存在'});    
        }else{    
            var request = new Request(str,function(err, rowCount){      
                if(err)err = {'err':err['message']};    
                callback(err,rows);    
              //  connection.close();    
            });    
                
            var n=0;                        
            request.on('row', function(columns) {                            //查询成功数据返回    
                rows[n]={};    
                columns.forEach(function(column) {    
                        rows[n][column.metadata.colName] = column.value;        //获取数据              
                });    
                n++;    
            });    
            
            connection.execSql(request);                                 //执行sql语句    
        }    
    });    
}    

}

client2.js：

const request = require(‘request-json’); var client = request.createClient(‘http://192.168.1.83:8081/’);

var mssql = require(’./tedious.js’); var conn = new mssql.mssql({ ‘userName’: ‘sa’, ‘password’: ‘123’, ‘server’: ‘localhost’, ‘options’: { ‘port’: 1433, ‘database’: ‘WEIGHT20’ } });

var lastId = 0; var timeBw = 1 * 1000;

class postData { _getDate(fc) {

    console.log('取称重数据 ID', lastId);
    var sql = 'SELECT top 1  * FROM \u79f0\u91cd\u4fe1\u606f  where \u5e8f\u53f7>' + lastId + ' order by \u5e8f\u53f7 ';
    console.log('SQL', sql);
    conn.query(sql, function (err, data) {
        if (!err) {
            //console.log(data)       //成功返回数据    
            fc(data);
        }
        else {
            fc([]);
            console.log(err)      //出错返回    
        }
    }
    );
}
_postDate(item, fc) {
    lastId = item['\u5e8f\u53f7'];
    var postData = {};
    postData['creator_id'] = item['\u5e8f\u53f7'];
    postData['weight_id'] = 'code002';
    postData['weight_code'] = 'code002';
    postData['weight_rfid'] = '0';
    postData['veh_id'] = item['\u6d41\u6c34\u53f7'];
    postData['car_no'] = item['\u8f66\u53f7'];
    postData['weight_gross'] = item['\u6bdb\u91cd'];
    postData['weight_veh'] = item['\u76ae\u91cd'];
    postData['weight_net'] = item['\u51c0\u91cd'];
    postData['garbage_type'] = item['\u8d27\u540d'];
    postData['weight_date'] = item['\u76ae\u91cd\u65f6\u95f4'];
    postData['delivery_unit'] = item['\u53d1\u8d27\u5355\u4f4d'];
    postData['prj_id'] = 2;
    postData['tcar_company_id'] = 0;
    postData['creator_id'] = item['\u5e8f\u53f7'];
    console.log('post data', postData);
    client.post('/jsonapi/cancu_weight/add.json',
        postData, function (err, res, body) {
            if (err) {
                console.error(err);
            }
            else {
                console.log('post resp', body);
                fc({ code: 0 });
            }
        });
}

_time(fc) {
    var _self = this;
    _self._getDate((d) => {
        if (d.length <= 0) {
            fc({ code: -1 });
            return;
        }
        _self._postDate(d[0], fc);
    })
}

run(fc) {
    var _self = this;
    _self._time(d => {
        setTimeout(function () {
            _self.run();
        }, timeBw);
    }, timeBw)
}

}

var t = new postData(); t.run();

请各位大佬指点