I implemented a controller class in Drupal 8, which redirects to an external site. If I use \Symfony\Component\HttpFoundation\RedirectResponse, I get this error.

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> Redirects to external URLs are not allowed by default, use \Drupal\Core\Routing\TrustedRedirectResponse for it.
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> 
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Using \Drupal\Core\Routing\TrustedRedirectResponse, I get this error.

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> The controller result claims to be providing relevant cache metadata, but leaked metadata was detected. Please ensure you are not rendering content too early.  
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>  Returned object class: \Drupal\Core\Routing\TrustedRedirectResponse
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> 
> 

What should I do?