Add documnetation

[sarim-zafar]

Hi, I stumbled upon you lib recently its been very helpful and i am very grateful that you have put such tremendous effort into making it but i find the documentation lacking for example i don't know how to assign a key to payload and receive its appropriate response from worker using the assigned id... This is only one of the many problems i have stumbled upon. I would be very grateful if you could add more documentation to readme file discussing various other functions Regards, Sarim

[kuangchanglang]

+1. expecting go-doc

[wellle]

I'm closing this as being pretty vague. Feel free to reopen with specific topics for which you feel like the documentation should be improved. :v: