AWS Amplify with Typescript and JS

import React, { useState, useEffect, createContext, useContext, ReactNode } from 'react'
import Amplify, { Auth, Hub } from 'aws-amplify'
import { CognitoUser } from '@aws-amplify/auth'
import { CognitoUserSession } from 'amazon-cognito-identity-js'
import { HubCallback } from '@aws-amplify/core/lib/Hub'
import IUser from '../../types/IUser'

interface IAuthContext {
  user: IUser | null
  login(username: string, password: string): Promise<CognitoUser>
  logout(): Promise<any>
}

interface Props {
  children?: ReactNode
}

Amplify.configure({
  Auth: {
    region: process.env.REACT_APP_AWS_REGION,
    userPoolId: process.env.REACT_APP_AWS_USER_POOL_ID,
    userPoolWebClientId: process.env.REACT_APP_AWS_USER_POOL_WEB_CLIENT_ID
  }
});

const login = (username: string, password: string): Promise<CognitoUser> => Auth.signIn(username, password)

const logout = (): Promise<any> => Auth.signOut()

const getSession = (): Promise<CognitoUserSession | null> => Auth.currentSession()

const useCognito = () => {
  const [user, setUser]  = useState<IUser | null>(null)
  const authListener: HubCallback = ({ payload: { event, data } }) => {
    switch (event) {
      case 'signIn':
        setUser({ username: data.username, token: data.signInUserSession.accessToken })
        break;
      case 'signOut':
          setUser(null);
        break;
    }
  }

  useEffect(() => {
    getSession().then((session) => {
      if(session && session.isValid()) {
        Auth.currentUserInfo().then((user: any ) => {
          setUser({username: user.username, token: session.getAccessToken()})
        })
      }
    })
  }, [])

  useEffect(() => {
    Hub.listen('auth', authListener)
    return () => Hub.remove('auth', authListener)
  }, [])

  return { user, login, logout }
}

const AuthContext = createContext<IAuthContext>({
  user: null,
  login,
  logout
})

export const useAuth = () => {
  return useContext(AuthContext)
};

export const Provider = ({ children }: Props) => {
  const auth = useCognito()
  return (<AuthContext.Provider value={auth}>{children}</AuthContext.Provider>)
}

@paulohfsantos, I share your curiosity about the IUser.
Given the information of setUser, we might intuit something like this:

type iUser {
  username: string, 
  token: CognitoAccessToken
}