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/pattern/fuzz.go

@@ -0,0 +1,51 @@
+//go:build gofuzz
+// +build gofuzz
+
+package pattern
+
+import (
+	"go/ast"
+	goparser "go/parser"
+	"go/token"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+var files []*ast.File
+
+func init() {
+	fset := token.NewFileSet()
+	filepath.Walk("/usr/lib/go/src", func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			// XXX error handling
+			panic(err)
+		}
+		if !strings.HasSuffix(path, ".go") {
+			return nil
+		}
+		f, err := goparser.ParseFile(fset, path, nil, 0)
+		if err != nil {
+			return nil
+		}
+		files = append(files, f)
+		return nil
+	})
+}
+
+func Fuzz(data []byte) int {
+	p := &Parser{}
+	pat, err := p.Parse(string(data))
+	if err != nil {
+		if strings.Contains(err.Error(), "internal error") {
+			panic(err)
+		}
+		return 0
+	}
+	_ = pat.Root.String()
+
+	for _, f := range files {
+		Match(pat.Root, f)
+	}
+	return 1
+}