New dht example for values storages

[rach-id]

The idea is to make a network where nodes can add values to the DHT (and not store them locally, a value should be stored in the closest node to its key) and others who have the keys (which for me are sha2-256 multihash) can retrieve these values.

So to get these nodes to be in the same network without having to hardcode the addresses etc. I found the pubsub pattern (the code im using is the pubsub example in the ipfs-camp-2019) that can give me this, and i found a DHT already defined there for routing.

This example uses Provide() to tell nodes that it has a certain CID and peers :

• Create a CID of the value i want to store
• Find the closest Peer to this CID by dht.GetClosestPeers()
• I take this peer and make a connection to it and send it the CID and the value (using the chat example)
• Each node has a local storage (i use a map for this) to store these values, so when it receives it, it adds to its local storage
• After adding the key:value to the storage, it executes dht.Provide()to announce that it has that entry
• Every node who wants this value and has the key, it executes dht.FindProviders()to find a peer having that, and it establishes a connection with it to retrieve the value from its local storage.