net: avoid darwin/arm64 platform bug in TestCloseWrite

On darwin_arm64, reading from a socket at the same time as the other
end is closing it will occasionally hang for 60 seconds before
returning ECONNRESET. (This is a macOS issue, not a Go issue.)

Work around this condition by adding a brief sleep before the read.

Fixes #49352 (we hope).
Updates #37795.

Change-Id: I4052aec21d311d7370550aea9dd7941f39141133
Reviewed-on: https://go-review.googlesource.com/c/go/+/414534
Run-TryBot: Bryan Mills <[email protected]>
Auto-Submit: Bryan Mills <[email protected]>
Reviewed-by: Damien Neil <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

src/net/net_test.go

@@ -97,6 +97,17 @@ func TestCloseWrite(t *testing.T) {
 					t.Error(err)
 					return
 				}
+
+				// Workaround for https://go.dev/issue/49352.
+				// On arm64 macOS (current as of macOS 12.4),
+				// reading from a socket at the same time as the client
+				// is closing it occasionally hangs for 60 seconds before
+				// returning ECONNRESET. Sleep for a bit to give the
+				// socket time to close before trying to read from it.
+				if runtime.GOOS == "darwin" && runtime.GOARCH == "arm64" {
+					time.Sleep(10 * time.Millisecond)
+				}
+
 				if !deadline.IsZero() {
 					c.SetDeadline(deadline)
 				}