ContactBitMask & Collisions

I am trying to make my game restart when two objects colliding. I tried coding it so it does that. I used print statements as placeholders just to see if its working correctly. They print when the two objects collide so I decided to replace it with code to change the position of the ball when they collide, it doesn't work now. I also tried creating a function to start the game over, that also doesn't work.

func didBegin(_ contact: SKPhysicsContact) {
        let contactMask = contact.bodyA.categoryBitMask | contact.bodyB.categoryBitMask

        if contactMask == PhysicsCategories.ballCategory | PhysicsCategories.dangerCategory {
            startGame()
        } else if contactMask == PhysicsCategories.ballCategory | PhysicsCategories.goalCategory {
            print("goal contact")
        }
    }

Main Code:

override func didMove(to view: SKView) {

        ball = self.childNode(withName: "ball") as! SKSpriteNode
        danger1 = self.childNode(withName: "danger1") as! SKSpriteNode
        danger2 = self.childNode(withName: "danger2") as! SKSpriteNode
        goal = self.childNode(withName: "goal") as! SKSpriteNode

        let border = SKPhysicsBody(edgeLoopFrom: self.frame)
        border.friction = 0
        border.restitution = 0

        danger1.physicsBody = SKPhysicsBody(rectangleOf: danger1.size)
        danger1.physicsBody?.categoryBitMask = PhysicsCategories.dangerCategory
        danger2.physicsBody = SKPhysicsBody(rectangleOf: danger2.size)
        danger2.physicsBody?.categoryBitMask = PhysicsCategories.dangerCategory

        ball.physicsBody = SKPhysicsBody(circleOfRadius: ball.size.width/2)
        ball.physicsBody?.categoryBitMask = PhysicsCategories.ballCategory
        ball.physicsBody?.contactTestBitMask = PhysicsCategories.dangerCategory
        ball.physicsBody?.collisionBitMask = PhysicsCategories.none

        goal.physicsBody = SKPhysicsBody(rectangleOf: goal.size)
        goal.physicsBody?.categoryBitMask = PhysicsCategories.goalCategory

        danger1.physicsBody?.isDynamic = false
        ball.physicsBody?.isDynamic = true
        goal.physicsBody?.isDynamic = false
        danger2.physicsBody?.isDynamic = false
        danger2.physicsBody!.affectedByGravity = false
        danger1.physicsBody!.affectedByGravity = false
        goal.physicsBody!.affectedByGravity = false
        ball.physicsBody!.affectedByGravity = false
        setupPhysics()
        startGame()
    }

settings.swift:

import SpriteKit

enum PhysicsCategories {
    static let none: UInt32 = 0
    static let ballCategory: UInt32 = 0x1           // 01
    static let dangerCategory: UInt32 = 0x1 << 1    // 10
    static let goalCategory: UInt32 = 0x1 << 2
}