Possible flake with unit test: TestReceiverReceive

[vaikas]

Describe the bug
https://prow.knative.dev/view/gcs/knative-prow/pr-logs/pull/knative_eventing/3212/pull-knative-eventing-unit-tests/1266085156708421633

Expected behavior
Test not to flake.

To Reproduce
Just seen this a few times while doing testing.

Knative release version
HEAD

Additional context
Add any other context about the problem here such as proposed priority

[vaikas]

From the head, you can repro this with:
go test -race -count=1000 -run ^TestReceiverReceive$ ./test/upgrade/prober/wathola/receiver/...

FAIL
FAIL	knative.dev/eventing/test/upgrade/prober/wathola/receiver	27.402s
FAIL

[vaikas]

Failures from the above tests:

{"level":"info","ts":1590694822.310598,"caller":"client/receiver.go:60","msg":"Listening for events on port 49152"}
{"level":"error","ts":1590694822.310925,"logger":"fallback","caller":"client/client.go:204","msg":"Error while opening the inbound connection: listen tcp :49152: bind: address already in use","stacktrace":"github.com/cloudevents/sdk-go/v2/client.(*ceClient).StartReceiver.func2\n\t/Users/vaikas/projects/go/pkg/mod/github.com/cloudevents/sdk-go/v2@v2.0.0/client/client.go:204"}
{"level":"info","ts":1590694822.313632,"caller":"client/receiver.go:63","msg":"Stopping event receiver on port 49152"}
--- FAIL: TestReceiverReceive (0.00s)
    services_test.go:64: 
        	Error Trace:	services_test.go:64
        	            				services_test.go:46
        	Error:      	Received unexpected error:
        	            	Post "http://localhost:49152/": dial tcp [::1]:49152: connect: connection refused
        	Test:       	TestReceiverReceive
    services_test.go:64: 
        	Error Trace:	services_test.go:64
        	            				services_test.go:47
        	Error:      	Received unexpected error:
        	            	Post "http://localhost:49152/": dial tcp [::1]:49152: connect: connection refused
        	Test:       	TestReceiverReceive
    services_test.go:51: 
        	Error Trace:	services_test.go:51
        	Error:      	Not equal: 
        	            	expected: 1
        	            	actual  : 0
        	Test:       	TestReceiverReceive
    services_test.go:52: 
        	Error Trace:	services_test.go:52
        	Error:      	Not equal: 
        	            	expected: 2
        	            	actual  : 1
        	Test:       	TestReceiverReceive
{"level":"info","ts":1590694822.314145,"caller":"config/reader.go:40","msg":"Define config file to be taken into account: /Users/vaikas/.config/wathola/config.toml"}
{"level":"info","ts":1590694822.3148758,"caller":"client/receiver.go:60","msg":"Listening for events on port 49163"}
{"level":"error","ts":1590694822.3151438,"logger":"fallback","caller":"client/client.go:204","msg":"Error while opening the inbound connection: listen tcp :49163: bind: address already in use","stacktrace":"github.com/cloudevents/sdk-go/v2/client.(*ceClient).StartReceiver.func2\n\t/Users/vaikas/projects/go/pkg/mod/github.com/cloudevents/sdk-go/v2@v2.0.0/client/client.go:204"}
{"level":"info","ts":1590694822.318367,"caller":"client/receiver.go:63","msg":"Stopping event receiver on port 49163"}
--- FAIL: TestReceiverReceive (0.00s)
    services_test.go:64: 
        	Error Trace:	services_test.go:64
        	            				services_test.go:46
        	Error:      	Received unexpected error:
        	            	Post "http://localhost:49163/": dial tcp [::1]:49163: connect: connection refused
        	Test:       	TestReceiverReceive
    services_test.go:64: 
        	Error Trace:	services_test.go:64
        	            				services_test.go:47
        	Error:      	Received unexpected error:
        	            	Post "http://localhost:49163/": dial tcp [::1]:49163: connect: connection refused
        	Test:       	TestReceiverReceive
    services_test.go:51: 
        	Error Trace:	services_test.go:51
        	Error:      	Not equal: 
        	            	expected: 1
        	            	actual  : 0
        	Test:       	TestReceiverReceive
    services_test.go:52: 
        	Error Trace:	services_test.go:52
        	Error:      	Not equal: 
        	            	expected: 2
        	            	actual  : 1
        	Test:       	TestReceiverReceive

[vaikas]

@cardil would you mind taking a looksie?

[cardil]

/assign @cardil