Wireless Diagnostics won't quit.

So the Wireless Diagnostics in my MacBook won't quit. It was on since yesterday morning and now I can't even restart my MacBook. What should I do? It kept on asking me to wait for the Wireless Diagnostics to finish but it won't even stop loading. I talked to the Apple support through chat and he said that I should try pressing the power button. I did what he told me and now that I am back to the Apple support, I can't even chat him because they're telling me that I should give them my number and wait for their call.