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/proxyman/outbound/handler.go

@@ -348,7 +348,7 @@ func (h *Handler) SetOutboundGateway(ctx context.Context, ob *session.Outbound)
 					errors.LogDebug(ctx, "use inbound source ip as sendthrough: ", inbound.Source.Address.String())
 				}
 			}
-		//case addr.Family().IsDomain():
+		// case addr.Family().IsDomain():
 		default:
 			ob.Gateway = addr
 
@@ -396,7 +396,6 @@ func (h *Handler) ProxySettings() *serial.TypedMessage {
 }
 
 func ParseRandomIP(addr net.Address, prefix string) net.Address {
-
 	_, ipnet, _ := net.ParseCIDR(addr.IP().String() + "/" + prefix)
 
 	ones, bits := ipnet.Mask.Size()