update session managemnent for unsecure cookie

[catatsuy]

This pull request includes several changes to the webapp/go module to enhance session management and update dependencies. The most important changes involve adding a new dependency, modifying the session store initialization, and updating the import statements.

Dependency Management:

• Added github.com/gorilla/securecookie v1.1.2 to the go.mod file and removed the redundant indirect requirement. (webapp/go/go.mod)

Session Management:

• Updated the import statements in main.go to include github.com/gorilla/securecookie. (webapp/go/main.go)
• Modified the session store initialization to use securecookie.CodecsFromPairs for enhanced security and set additional session options. (webapp/go/main.go)
• Removed the line setting session.Options.Secure to false in the getSession function, as this is now managed by the session store options. (webapp/go/main.go)