lint: fix all major issues

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

util/buf/buf.go

@@ -8,11 +8,13 @@ type buffer struct {
 	*bytes.Buffer
 }
 
+// Close reset buffer contents
 func (b *buffer) Close() error {
 	b.Buffer.Reset()
 	return nil
 }
 
+// New creates new buffer that satisfies Closer interface
 func New(b *bytes.Buffer) *buffer {
 	if b == nil {
 		b = bytes.NewBuffer(nil)