net/http: wrong error returned when request canceled via context after CL 546676 ("net/http: simplify HTTP/1 request cancelation"); detected via x/build/buildlet.TestExecTimeoutError failing

[dmitshur]

As visible on the x/build by Go commit view, TestExecTimeoutError has started to fail consistently at Go tip starting with CL 546676:

=== RUN   TestExecTimeoutError
    buildletclient_test.go:210: cl.Exec error = error copying response: net/http: request canceled; want buildlet: timeout waiting for command to complete
--- FAIL: TestExecTimeoutError (0.00s)

This code in x/build hasn't changed in a long time. Either the test (or what it's testing) in x/build has a problem that is uncovered by the net/http change, otherwise this is a problem in net/http.

CC @neild.

[gopherbot]

Change https://go.dev/cl/586077 mentions this issue: buildlet: don't rely on io.Copy error to be context.DeadlineExceeded

[dmitshur]

I sent CL 586077 which fixes the immediate problem on the x/build side. It'd be good for Damien to check if this is working as expected.

[gopherbot]

Change https://go.dev/cl/586315 mentions this issue: net/http: return correct error when reading from a canceled request body