HowTo: Implement user sign up and login with AWS Cognito

getUserCredentials.js

async function getUserCredentials(idToken) {
  const cognitoidentity = new AWS.CognitoIdentity()

  const providerName = `cognito-idp.${process.env.AWS_REGION}.amazonaws.com/${process.env.USER_POOL_ID}`
  let response = await cognitoidentity.getId({
    IdentityPoolId: process.env.IDENTITY_POOL_ID,
    Logins: {
      [providerName]: idToken
    }
  }).promise()

  const identityId = response.IdentityId
  response = await cognitoidentity.getCredentialsForIdentity({
    IdentityId: identityId,
    Logins: {
      [providerName]: idToken
    }
  }).promise()
  
  const credentials = new AWS.Credentials(
    response.Credentials.AccessKeyId,
    response.Credentials.SecretKey,
    response.Credentials.SessionToken
  )

  return {
    identityId,
    credentials
  }
}