diff --git a/common/common.go b/common/common.go
new file mode 100644
index 0000000..22a633c
--- /dev/null
+++ b/common/common.go
@@ -0,0 +1,13 @@
+package common
+
+import "os"
+
+// GetenvDefault retrieves an environment variable if set, or a provided default
+func GetenvDefault(key string, d string) string {
+	val, ok := os.LookupEnv(key)
+	if ok {
+		return val
+	} else {
+		return d
+	}
+}
diff --git a/common/common_test.go b/common/common_test.go
new file mode 100644
index 0000000..9376b1e
--- /dev/null
+++ b/common/common_test.go
@@ -0,0 +1,39 @@
+package common
+
+import (
+	"os"
+	"testing"
+)
+
+var testEnvKey string = "TEST_MQTT_KEY"
+
+func assertError(t testing.TB, got, want string) {
+	t.Helper()
+	if got != want {
+		t.Errorf("Error: got '%s', want '%s'", got, want)
+	}
+}
+
+func TestGetenvDefault(t *testing.T) {
+	t.Run("key not set", func(t *testing.T) {
+		originalEnv := os.Getenv(testEnvKey)
+		os.Unsetenv(testEnvKey)
+		defer os.Setenv(testEnvKey, originalEnv)
+
+		got := GetenvDefault(testEnvKey, "found")
+		want := "found"
+
+		assertError(t, got, want)
+	})
+
+	t.Run("key set", func(t *testing.T) {
+		originalEnv := os.Getenv(testEnvKey)
+		os.Setenv(testEnvKey, "batman")
+		defer os.Setenv(testEnvKey, originalEnv)
+
+		got := GetenvDefault(testEnvKey, "found")
+		want := "batman"
+		assertError(t, got, want)
+
+	})
+}