fix(contrib slog/logrus): fix for shuffle testing

Fix slog and logrus to pass their test suite when shuffle testing is
enabled. In particular, fix the following two test invocations.

go test -test.shuffle 1761195191840193457 ./contrib/log/slog/
go test -test.shuffle 176139568378992735 ./contrib/sirupsen/logrus/ -count 2

Author: felixge

contrib/log/slog/slog_test.go

@@ -84,6 +84,8 @@ func testLogger(t *testing.T, createLogger func(b io.Writer) *slog.Logger, asser
 	spanID := strconv.FormatUint(span.Context().SpanID(), 10)
 	if os.Getenv("DD_TRACE_128_BIT_TRACEID_LOGGING_ENABLED") == "false" {
 		// Re-initialize to account for race condition between setting env var in the test and reading it in the contrib
+		oldCfg := cfg
+		t.Cleanup(func() { cfg = oldCfg })
 		cfg = newConfig()
 		traceID = strconv.FormatUint(span.Context().TraceIDLower(), 10)
 	} else {

contrib/sirupsen/logrus/logrus_test.go

@@ -36,6 +36,8 @@ func TestFire128BitDisabled(t *testing.T) {
 	t.Setenv("DD_TRACE_128_BIT_TRACEID_LOGGING_ENABLED", "false")
 
 	// Re-initialize to account for race condition between setting env var in the test and reading it in the contrib
+	oldCfg := cfg
+	t.Cleanup(func() { cfg = oldCfg })
 	cfg = newConfig()
 
 	tracer.Start()