come by—pay an informal visit:
- Why don’t you come by some afternoon and have coffee with me.
go by—
1. (of time) pass:
- Less than a day on the job goes by before the announcement comes that the workers are, once again, on strike.
2. (of an opportunity, etc.) pass without being taken:
- Often the chance goes by, or the trail followed proves false.
3. (of a fault, etc.) be ignored:
- I know you were late again this morning, but we’ll let that go by.