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/lock.go

@@ -18,7 +18,7 @@ import (
 func (s *script) lock(lockfile string) (func() error, error) {
 	start := time.Now()
 	defer func() {
-		s.stats.LockedTime = time.Now().Sub(start)
+		s.stats.LockedTime = time.Since(start)
 	}()
 
 	retry := time.NewTicker(5 * time.Second)