GitLab

shadow err

This reverts commit a011832acc5d8d1bd013da9d1422f9f497989ede.

Do not remove tests that reveal race conditions.

- setting the error is moved into the preamble
- we call the preamble before the err!=nil branch because we send to the conn in there

- always return command errors in Next, neven in Send
- also check trailer when receiving EOF
- update tests to reflect changes