strange locks on PG 11 with Golang programs

We are lately experiencing very strange locks on PostgreSQL 11.7 when we
process ETL tasks using our programs in Go 1.13.8 using standard libraries
sql and pq.

ETL task has to rename tables but PostgreSQL shows that this simple
operation waits for Lock on relation and select from PG wiki (
https://wiki.postgresql.org/wiki/Lock_Monitoring) which should show
blocking process shows that command "alter table .... rename to ...." is
blocked by process "COPY .... to stdout" but from completely different
table.

And from time to time even selects from some tables seem to by blocked by
copy commands running on other tables. This is shown by the same select
from PG wiki for blocking queries.

All this stuff runs from golang programs. So maybe problem is not on
PostgreSQL but in golang libraries?

Thank you for any suggestions

Josef Machytka

Berlin