Cleanup: Lint warnings and deprecated packages (#263)

* Fix lint warnings and std lib deprecations

* Replace deprecated std lib with maintained drop-in replacement fork

Backwartds compatible with original package and suggested by std lib due to security and stability issues.

* OAuth2 is now a direct dependency due to Dropbox

* Undo change

* Revert "Replace deprecated std lib with maintained drop-in replacement fork"

This reverts commit 2887bd409f.

* Update channel handling

* Add linter for PRs

* Rename CI, fetch all issues, add govet

cmd/backup/main.go

@@ -15,7 +15,7 @@ func main() {
 	}
 
 	unlock, err := s.lock("/var/lock/dockervolumebackup.lock")
-	defer unlock()
+	defer s.must(unlock())
 	s.must(err)
 
 	defer func() {
@@ -34,7 +34,6 @@ func main() {
 		if err := s.runHooks(nil); err != nil {
 			s.logger.Error(
 				fmt.Sprintf(
-
 					"Backup procedure ran successfully, but an error ocurred calling the registered hooks: %v",
 					err,
 				),