Flaky test: TestSendError

[crazy-max]

Encountered this one in #218: https://github.com/tonistiigi/fsutil/actions/runs/11671808580/job/32499037261#step:4:445

#18 15.02 === RUN   TestSendError
#18 15.02     receive_test.go:47: 
#18 15.02         	Error Trace:	/src/receive_test.go:47
#18 15.02         	            				/go/pkg/mod/golang.org/x/[email protected]/errgroup/errgroup.go:75
#18 15.02         	            				/usr/local/go/src/runtime/asm_amd64.s:1700
#18 15.02         	Error:      	"context canceled" does not contain "error from sender:"
#18 15.02         	Test:       	TestSendError
#18 15.02     receive_test.go:48: 
#18 15.02         	Error Trace:	/src/receive_test.go:48
#18 15.02         	            				/go/pkg/mod/golang.org/x/[email protected]/errgroup/errgroup.go:75
#18 15.02         	            				/usr/local/go/src/runtime/asm_amd64.s:1700
#18 15.02         	Error:      	"context canceled" does not contain "foo bar"
#18 15.02         	Test:       	TestSendError

[crazy-max]

Looks quite flaky, happened again on master: https://github.com/tonistiigi/fsutil/actions/runs/11672244797/job/32500428202#step:4:436