[Bacardi]

what if you remove double quotes \" \" ?

*update
Not work in this game mode (custom/custom)

Spoiler

Just make sure:
...csgo/gamemodes_a.txt
-gamemodes_serverfile gamemodes_a.txt

and reboot or launch server.

Again, you should see "exec" files using command on server console (not client):

] rcon sv_game_mode_convars
exec {
  exec gamemode_myfile.cfg
  exec gamemode_myfile_server.cfg
}
GameTypes: dumping convars for bot difficulty (none:0):convars {
  bot_difficulty int( 0 = 0x0 )
  bot_dont_shoot int( 1 = 0x1 )
  bot_quota int( 0 = 0x0 )
}

*edit
Testing again, there could be something fishy going on. Could it be it not work ? I need test again.

[Bacardi]

OK. Sorry double post.

Turns out, why my previous gamemodes example didn't work, even game shows those current "exec" config files.
Answer is:
In this specific game type and mode (custom/custom), game not execute any "exec" files from gamemodes structure.

However, in other modes like casual for example it works.

-----------------

Try new way.

If you continue custom game mode, you need fiddle with less files:
- Forget -gamemodes_serverfile and new gamemodes_*.txt
- Use cvar servercfgfile to change default server.cfg file to else.
- Add all your cvars in your server config file. Start using your server config file only.

With gamemodes_server.txt :
- You can change "maxplayers" size, when server is not launched with -maxplayers_override
- You can create custom map groups.

gamemodes_server.txt

"GameModes_Server.txt"
{
	"gameTypes"
	{
		"custom"
		{
	
			"gameModes"
			{
				"custom"
				{
					"maxplayers"		"60"
	
					// Custom/custom game mode do not exec any files. Use server.cfg or file set into cvar servercfgfile
					"exec"
					{
						//"exec" "gamemode_myfile.cfg"
						//"exec" "gamemode_myfile_server.cfg"
					}

					"mapgroupsSP"
					{
						"empty"		"" // This line just removes one log message from console
					}
				}
			}
		}
	}

	"mapgroups"
	{
		"mg_mymapgroup"
		{
			"maps"
			{
				"de_dust2"		""
				"cs_office"		""
			}
		}
	}

	"mg_mymapgroup2"
	{
		"maps"
		{
			"de_dust2"		""
			"cs_office"		""
		}
	}
}

[BlackFart]

Really, thank you for your time I'm going to test what you said and edit this post in 1-2 hours

EDIT:
Ok, I tried with a deathmatch mode... And it looks like to work !
I'm going to try with both servers up to be sure
Thank you a lot

EDIT:
It works with both <3
Thank you for your time.

For those with the same issue, I did what Bacardi asked me to do, but with a gametype/mode at 1/2