replace dep with go modules (#16017)

- guide shamelessly stolen from prometheus/prometheus
- updates local interface of oauth exchange
- updates local impl of hclogger
- bump jaeger client version

closes #16088

vendor/github.com/gorilla/websocket/prepared.go

@@ -19,7 +19,6 @@ import (
 type PreparedMessage struct {
 	messageType int
 	data        []byte
-	err         error
 	mu          sync.Mutex
 	frames      map[prepareKey]*preparedFrame
 }