Help me! Solution for double jump for character 2d

Hello and sorry for my English.
I'm beginning. I'm trying to create a double jump feature.
My logic is:
- Jump method called in FixedUpdate
- The method to assign _canJump = true and GetButtonDown, called in Update method
Everything is good for a single jump, but double jump not working.
This is my solution. It looks very bad.




Someone can give me a solution for this.
I want everything related to physics placed in FixedUpdate.
Thanks.