如何将 pg-promise 与 connect-pg-simple 连接起来？

Question

我已经通过 const db = require('./config/db'); 文件建立了连接，并且 conn 工作正常但是使用 connect-pg-simple 我有一个错误。 error: there is no unique or exclusion constraint matching the ON CONFLICT specification at Parser.parseErrorMessage 这是代码..

const db = require('./config/db');
var pg = require('pg'),
  session = require('express-session'),
  pgSession = require('connect-pg-simple')(session);

var pgPool = db.$pool;
app.use(
  session({
    store: new pgSession({
      pool: pgPool, // Connection pool
      tableName: 'session' // Use another table-name than the default "session" one
    }),
    secret: 'cat',
    resave: false,
    saveUninitialized: true,
    cookie: { maxAge: 30 * 24 * 60 * 60 * 1000 } // 30 days
  })
);```
I do not know ` db.$pool` is right or wrong ?