npm install --save swagger-ui-express

import swaggerUI = require('swagger-ui-express')
import swDocument from './openapi'
...
app.use('/api-docs',swaggerUI.serve,swaggerUI.setup(swDocument))

import {swLoginRoute} from './routes/login'
const swagger = {
  openapi: '3.0.0',
  info: {
    title: 'Express API for Dangle',
    version: '1.0.0',
    description: 'The REST API for Dangle Panel service'
  },
  servers: [
    {
      url: 'http://localhost:3001',
      description: 'Development server'
    }
  ],
  paths: {
    ...swLoginRoute
  },
}
export default swagger

import {swGetUserInfo} from './get-user-info'
import {swUpdateInfo} from './update-info'
export const swLoginRoute = {
  "/login": {
    "get": {
      ...swGetUserInfo
    },
    "patch": {
      ...swUpdateInfo
    }
  }
}

import schema, {joiSchema} from './update-info.spec/schema'
export const swUpdateInfo = {
  "summary": "update the user info",
  "tags": [
    "login"
  ],
  "parameters": [
    {
      "name": "key",
      "in": "header",
      "schema": {
        "type": "string"
      },
      "required": true
    }
  ],
  "requestBody": {
    "content": {
      "application/json": {
        "schema": {
          ...schema
        }
      }
    }
  },
  "responses": {
    "200": {
      "description": "Done"
    },
    "default": {
      "description": "Error message"
    }
  }
}
// ...далее идёт код роута

"schema": {
  ...schema
}

await joiSchema.validateAsync(req.body)

npm install --save joi joi-to-swagger

const joi = require('joi')
const j2s = require('joi-to-swagger')
// Joi
export const joiSchema = joi.object().keys({
  mode:    joi.string().required(),
  email:   joi.string().email()
})
// end of Joi
const schema = j2s(joiSchema).swagger
export default schema

npm install --save-dev gulp @babel/register @babel/plugin-proposal-class-properties @babel/preset-env @babel/preset-typescript

const gulp = require('gulp')
const through = require('through2')
import { compile } from 'json-schema-to-typescript'
const fs = require('fs')
const endName = "schema.ts"
const routes = `./routes/**/*.spec/*${endName}`
function path(str: string) : string
{
   let base = str
   if(base.lastIndexOf(endName) != -1)
     base = base.substring(0, base.lastIndexOf(endName))
   return base
}
gulp.task('schema', () => {
  return gulp.src(routes)
    .pipe(through.obj((chunk, enc, cb) => {
      const filename = chunk.path
      import(filename).then(schema => { // dynamic import
        console.log('Converting', filename)
        compile(schema.default, `IDTO`)
          .then(ts => {
            //console.log(path(filename).concat('interface.ts'), ts)
            fs.writeFileSync(path(filename).concat('interface.ts'), ts)
          })
        })
      cb(null, chunk)
    }))
})
// watch service
const { watch, series } = require('gulp')
exports.default = function() {
  watch(routes, series('schema'))
}