looks like i do it wrong. I turned auto_explain on with adding next valued to postgresql.conf:
shared_preload_libraries = 'pg_stat_statements,pg_wait_sampling,pg_stat_kcache,auto_explain' auto_explain.log_min_duration = '3s'
in my monitoring I can see long running queries that exceeded limit of 3s and successfully finished.
But when I look into my log 'postgresql-Mon.log' (and next days) there is nothing about those queries. Only a few strings about modules during database startup process.
Am I missing something?