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/printf/fuzz.go

@@ -0,0 +1,12 @@
+//go:build gofuzz
+// +build gofuzz
+
+package printf
+
+func Fuzz(data []byte) int {
+	_, err := Parse(string(data))
+	if err == nil {
+		return 1
+	}
+	return 0
+}