staticcheck (#313)

* CI: use staticcheck for linting

This commit switches the linter for Go code from golint to staticcheck.
Golint has been deprecated since last year and staticcheck is a
recommended replacement.

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

* revendor

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

* cmd,pkg: fix lint warnings

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

vendor/honnef.co/go/tools/lintcmd/stats.go

@@ -0,0 +1,8 @@
+//go:build !aix && !android && !darwin && !dragonfly && !freebsd && !linux && !netbsd && !openbsd && !solaris
+// +build !aix,!android,!darwin,!dragonfly,!freebsd,!linux,!netbsd,!openbsd,!solaris
+
+package lintcmd
+
+import "os"
+
+var infoSignals = []os.Signal{}