## What happened
A Go project (A) depended on another private GitHub repository (B), and the Cloud Build pipeline could not fetch it. `glide install` failed with: [WARN] Unable to checkout github.com/avi/api, [ERROR] Update failed for github.com/avi/api: Unable to get repository. Cloning directly with the git builder failed too: SSH clone failed with "Host key verification failed / Could not read from remote repository", and HTTPS clone failed with "could not read Username for 'https://github.com': No such device or address". The build service account had no credentials for GitHub.
## The fix that worked
Cloud Build steps have no GitHub credentials by default, so private repos are unreachable until you inject them. The recommended approach is to store a deploy key or token encrypted and pull it into the build: keep the SSH key in Cloud Storage, fetch it in an early build step, then use it for git operations (add GitHub to known_hosts to avoid the host-key verification failure). Google published a tutorial on using encrypted files in builds covering exactly this pattern. This resolved the reporter's glide/private-repo failures.