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/analysis/code/visit.go

@@ -0,0 +1,51 @@
+package code
+
+import (
+	"bytes"
+	"go/ast"
+	"go/format"
+
+	"honnef.co/go/tools/pattern"
+
+	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/analysis/passes/inspect"
+	"golang.org/x/tools/go/ast/inspector"
+)
+
+func Preorder(pass *analysis.Pass, fn func(ast.Node), types ...ast.Node) {
+	pass.ResultOf[inspect.Analyzer].(*inspector.Inspector).Preorder(types, fn)
+}
+
+func PreorderStack(pass *analysis.Pass, fn func(ast.Node, []ast.Node), types ...ast.Node) {
+	pass.ResultOf[inspect.Analyzer].(*inspector.Inspector).WithStack(types, func(n ast.Node, push bool, stack []ast.Node) (proceed bool) {
+		if push {
+			fn(n, stack)
+		}
+		return true
+	})
+}
+
+func Match(pass *analysis.Pass, q pattern.Pattern, node ast.Node) (*pattern.Matcher, bool) {
+	// Note that we ignore q.Relevant – callers of Match usually use
+	// AST inspectors that already filter on nodes we're interested
+	// in.
+	m := &pattern.Matcher{TypesInfo: pass.TypesInfo}
+	ok := m.Match(q.Root, node)
+	return m, ok
+}
+
+func MatchAndEdit(pass *analysis.Pass, before, after pattern.Pattern, node ast.Node) (*pattern.Matcher, []analysis.TextEdit, bool) {
+	m, ok := Match(pass, before, node)
+	if !ok {
+		return m, nil, false
+	}
+	r := pattern.NodeToAST(after.Root, m.State)
+	buf := &bytes.Buffer{}
+	format.Node(buf, pass.Fset, r)
+	edit := []analysis.TextEdit{{
+		Pos:     node.Pos(),
+		End:     node.End(),
+		NewText: buf.Bytes(),
+	}}
+	return m, edit, true
+}