socket is being accessed in the function body, hence the need to include it in the function head.
Current:
def maybe_track_user(

•     product,*
  

•     %{assigns: %{live_action: :show, user_token: user_token}}*
  

•     ) do*
  

•            if connected?(socket) do*
  

•            user = Accounts.get_user_by_session_token(user_token)*
  

•            # do tracking here!*
  

• end*

Expected:
def maybe_track_user(

•  product,*
  

•  %{assigns: %{live_action: :show, user_token: user_token}} **= socket***
  

•  ) do*
  

•          if connected?(socket) do*
  

•          user = Accounts.get_user_by_session_token(user_token)*
  

•         # do tracking here!*
  

end

Title: Programming Phoenix LiveView: B3.0: Include “=socket” in function header (page 255)
Example: Programming Flutter - ‘pub get’ command not working (page 15)

Please also add the book’s tag if it has not already present, thanks!