The coinjoin protocol is based on Bitcoin's Proof-of-Stake (PoS) protocol. It allows miners to mine blocks at a low cost, without having to worry about fees, which are a problem for Bitcoin. This is a good thing, because it makes it easier for miners to mine blocks faster and more profit is made from the block mining.
Mister, It looks like you have got a lot of things mixed up here. Where did you get it from?
Proof of stake is something completely different from coinjoin. And Bitcoin has never used PoS, and it's less likely that it will use that protocol
I'm a bit confused about the concept of coinjoin. Is it possible to implement it
I suggest you do more reading about coinjoin,
proof of work and then proof of stake. Start with the link that has been provided to you in the comment above mine.