Timeout when exporting world-wide data

Nobody has claimed this yet.

I am currently trying to export a dataset worldwide, but there are large areas without data. So I don't have anything data where the oceans are f.e.
All of my queries (postgres) are fast. I did debug my setting a log for queries that take too long.
Still I get an error when trying to export

```
/usr/local/lib/node_modules/tilelive/bin/tilelive-copy:100
if (err) throw err;
^

Error: Copy operation timed out
at Timeout. (/usr/local/lib/node_modules/tilelive/lib/tilelive.js:390:22)
at Timeout.wrapper (timers.js:408:11)
at tryOnTimeout (timers.js:224:11)
at Timer.listOnTimeout (timers.js:198:5)
```

The theory with the oceans is just because my dataset is still empty when I view what was exported until the timeout. It's an empty mbtiles file. Is that possible? Or what other cause could my timeout have? How can I get more debug information? Any idea?
I am using `tilelive-copy` in docker btw.

Start by reproducing the worldwide export with tilelive-copy in Docker, then inspect the timeout reported in tilelive/lib/tilelive.js:390 and the command entry at tilelive-copy:100. Compare the run with the PostgreSQL query logs and gather additional diagnostics. Done means identifying the timeout cause and confirming a completed export or documenting the blocking failure.

Written by the indexing model from the issue text.