git-clone with ssh-key fails

{"level":"error","ts":1668687926.8676572,"caller":"git/git.go:55","msg":"Error running git [fetch --recurse-submodules=yes --depth=1 origin --update-head-ok --force ]: exit status 128\nCould not create directory '/home/nonroot/.ssh'.\r\nFailed to add the host to the list of known hosts (/home/nonroot/.ssh/known_hosts).\r\ngit@github.com: Permission denied (publickey).\r\nfatal: Could not read from remote repository.\n\nPlease make sure you have the correct access rights\nand the repository exists.\n","stacktrace":"github.com/tektoncd/pipeline/pkg/git.run\n\t/go/src/github.com/tektoncd/pipeline/pkg/git/git.go:55\ngithub.com/tektoncd/pipeline/pkg/git.Fetch\n\t/go/src/github.com/tektoncd/pipeline/pkg/git/git.go:158\nmain.main\n\t/go/src/github.com/tektoncd/pipeline/cmd/git-init/main.go:53\nruntime.main\n\t/usr/lib/golang/src/runtime/proc.go:255"}
{"level":"fatal","ts":1668687926.8677328,"caller":"git-init/main.go:54","msg":"Error fetching git repository: failed to fetch []: exit status 128","stacktrace":"main.main\n\t/go/src/github.com/tektoncd/pipeline/cmd/git-init/main.go:54\nruntime.main\n\t/usr/lib/golang/src/runtime/proc.go:255"}