format code with gofumpt

gofumpt (https://github.com/mvdan/gofumpt) provides a supserset of `gofmt` / `go fmt`,
and addresses various formatting issues that linters may be checking for.

We can consider enabling the `gofumpt` linter to verify the formatting in CI, although
not every developer may have it installed, so for now this runs it once to get formatting
in shape.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

notifications/http_test.go

@@ -197,7 +197,6 @@ func TestHTTPSink(t *testing.T) {
 	if err := sink.Close(); err == nil {
 		t.Fatalf("second close should have returned error: %v", err)
 	}
-
 }
 
 func createTestEvent(action, repo, typ string) Event {