title: how to renew expired certificate with fastlane?
body: <p>My iOS certificate is stored in GitHub and it is expired, the failure message in circleci progress is that ‘Your certificate 'xxxxxxx.cer' is not valid, please check end date and renew it if necessary’. </p>
  
  <p>Do I need to create a new certificate, or download an existing one? I don’t remember how this was originally created, I thought it was done by Fastlane as part of the build.</p>
  
  <p>But I don't know how to modify the Fastlane command, I have tried to add the 'cert', but it fails.</p>