How do I put a player's name in a /title command? in JE 1.12.2 [duplicate]

like the title says, I'm looking for a way to display a player name in a /tellraw command which is run by a command block. Example:

/tellraw @a {"text":"","extra":[{"text":"A player has won the game!","color":"blue"}]}

And the output is something like this:

A player has won the game!

But I want the output to be something like

JasonSPQR has won the game!

Using the @p parameter

Tellraw allows for a "selector" part, which takes any selector you want and displays a name. You should do:

/tellraw @a {"text":"","color":"blue","extra":[{"selector":"@p"},{"text":" has won the game!"}]}

This will only work in 1.8 snapshots and above. There is no way to do this in older versions.