panic on k8s API timeouts

[mazay]

Describe the bug

{"@timestamp":"2022-01-25T05:08:05Z","app":"s3sync-service","level":"error","message":"etcdserver: request timed out","version":"devel"}
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x38 pc=0x1555b77]

goroutine 29 [running]:
github.com/mazay/s3sync-service/service.(*Config).setDefaults(...)
	/go/src/github.com/mazay/s3sync-service/service/config.go:62
github.com/mazay/s3sync-service/service.readConfigString(0x0, 0x0, 0x7ffc805b7383)
	/go/src/github.com/mazay/s3sync-service/service/config.go:168 +0xb7
github.com/mazay/s3sync-service/service.getConfig(0xc000653eb8)
	/go/src/github.com/mazay/s3sync-service/service/config.go:133 +0xab
github.com/mazay/s3sync-service/service.Start.func1(0xc00007f260, 0xc00007f2c0, 0xc00007f200, 0xc00007f320, 0xc00007f1a0, 0xc00007f140, 0xc00007f0e0)
	/go/src/github.com/mazay/s3sync-service/service/main.go:181 +0x9a5
created by github.com/mazay/s3sync-service/service.Start
	/go/src/github.com/mazay/s3sync-service/service/main.go:158 +0x65f

To Reproduce
Steps to reproduce the behaviour:

1. Run on k8s with configmap integration
2. Take one of the k8s masters out (eg. reboot)
3. See the above error

Expected behaviour
The app should keep running and properly handle API glitches.

Environment (please complete the following information):

• OS: k3s
• Version: v1.22.5+k3s1