As known, a map can't be accessed with read/write concurrently on
multiple goroutines. This just replaces all uses of global maps for
caches with sync.Map, which is safe to be used concurrently.
Some databases (maybe all of them) will set the database column
names to lowercase.
This was problematic because we needed to match these names
with the ksql tags, which were not lowercased.
Now we support both versions, lowercased or not.