go test -vnow streamst.Logoutput as it happens, rather than at the end of all tests.
Finally!
Previously t.Log() and t.Logf() buffer the output till the end of a test, which was surprising. That forced me to use fmt.Printf() or whatever a logger available.
The issue has been opened since 2018 and it has finally landed on Go 1.14.
Source: posts/2020/t-log.md