Offline session key agreement protocol Is there any implemented solution to agree on a session key in offline way.

I can exchange some keys before being offline but I need both sides to create the session key offline.

I need implemented and secure solutions.
Given the information in the question and in the comments, this is pretty straightforward:


Online phase: Use any common key agreement protocol, e.g. Diffie-Hellmann key exchange to generate a shared secret. 
Offline phase: Use a proper key derivation function on the shared secret and a nonce - one nonce for each key you need to generate. A counter would also work.



  I need implemented and secure solutions.


Both functionalities should be included in various cryptographic libraries. 

For the security it is necessary to make sure that the shared secret is stored securely. But that's basic key management.

For the security proof you could argue that the KDF is actually a PRF or use the properties of one-way functions. A proof by contradiction should only take a few lines.