const useThirdPartyAuthSdk = loadable.hook(() => 'some-large-sdk')
...

const useUserSignIn = () => {
  // 'some-large-sdk' is not loaded until this hook is ran
  const thirdPartyAuthSdk = useThirdPartyAuthSdk()
  const signin = React.useCallback(creds => {
    if (!thirdPartyAuthSdk) throw new Error('Auth SDK used before ready')
    thirdPartyAuthSdk.initiateSignin(creds)
  }, [thirdPartyAuthSdk])
  return {
    ready: !!thirdPartyAuthSdk,
    signin
  }
}