GitHub Action CI: Add Go source file format check (#6090)

https://github.com/XTLS/Xray-core/pull/6057#issuecomment-4364819830

And https://github.com/XTLS/Xray-core/pull/6149#issuecomment-4546876261

app/observatory/burst/burstobserver.go

@@ -2,7 +2,6 @@ package burst
 
 import (
 	"context"
-
 	"sync"
 
 	"github.com/xtls/xray-core/app/observatory"
@@ -72,7 +71,6 @@ func (o *Observer) Start() error {
 		o.hp.StartScheduler(func() ([]string, error) {
 			hs, ok := o.ohm.(outbound.HandlerSelector)
 			if !ok {
-
 				return nil, errors.New("outbound.Manager is not a HandlerSelector")
 			}