troubleshooting "idle in transaction"

Greetings..

I'm running 8.0.12 and the system has been very stable for years now with no
significant application changes. I am using Apache::Session::Postgres in a web
application to store session state. This has really been flawless for us so
far, but lately I've caught a few occurrences where I will see in GNU top, the
following:

9136 postgres 16 0 546m 9.8m 8080 S 0 0.0 0:00.00 1 postgres:
postgres sessions harvard(49197) idle in transaction
10892 postgres 16 0 546m 9180 7356 S 0 0.0 0:00.01 3 postgres:
postgres sessions harvard(49649) SELECT waiting
12174 postgres 16 0 546m 9172 7348 S 0 0.0 0:00.00 3 postgres:
postgres sessions harvard(51158) SELECT waiting
12175 postgres 16 0 546m 9152 7328 S 0 0.0 0:00.01 1 postgres:
postgres sessions harvard(51159) SELECT waiting
12176 postgres 16 0 546m 9112 7288 S 0 0.0 0:00.01 1 postgres:
postgres sessions harvard(51160) SELECT waiting

I can connect to the database fine and select from it when this occurs, but I'm
guessing that the owner of that particular session row is refreshing their
browser and seeing it 'hang', causing the lock jam. I know this could
potentially be a problem with Apache::Session logic, but that module has not
been updated for as long as I can remember, so I'm wondering if this could be a
database issue somehow?

Previously, I have just killed the process that's idle in transaction, then
things clean up.. However, this doesn't feel very clean.

Can anyone recommend a good process for learning why exactly that transaction is
not completing? Or, is there a postgresql.conf setting that can automatically
kill these errant locks?

-Dan