Jumping is typically handled by giving some additional values to the player state, a velocity and/or acceleration depending on your games complexity. You want to process the jump asynchonously, allowing the standard game loop to continue while the player is jumping.

Your jump function, if you got it to work, would be quite limited. The player could only jump straight up or down, but could not jump in a parabola.

You will need to add conditions to the rest of your code to prevent, for example, the player walking while jumping, again depending on the game (some games allow the player limited control of the character even in the air). You might need to record whether the player is on the ground or jumping with a boolean condition variable. You will want some collision detection to determine if the player hits the ceiling (if any), other characters and when it hits the ground again.