How can I send a message to all players in the minecraft server?

Currently I am hosting a minecraft server, and I as the operator would like to send a "server message", so all the players can read it, instead of me sending the message specifically to each and every player. How can this be done? I looked online, but they all suggest the /msg keyword, which does not work anymore.

You'd want to use say:

  say <message …>

Fails if any target selectors do not resolve to at least one online player, or if any named players are not online.

On success, broadcasts message to all players on the server. If a multi-person target selector (e.g., @a) is used in message, the list of names is formatted as "name1 and name2" for two players, or "name1, name2, ... and nameN" for N players. Target selectors are not recognized in Pocket Edition.

For example: say Hello world

https://minecraft.gamepedia.com/Commands/say

Just press t and type the message and press enter