Bug fix: Key delimiters are now case insensitive

viper.go

@@ -1464,10 +1464,12 @@ func Set(key string, value any) { v.Set(key, value) }
 
 func (v *Viper) Set(key string, value any) {
 	// If alias passed in, then set the proper override
+
 	key = v.realKey(strings.ToLower(key))
 	value = toCaseInsensitiveValue(value)
 
-	path := strings.Split(key, v.keyDelim)
+	path := strings.Split(key, strings.ToLower(v.keyDelim))
+
 	lastKey := strings.ToLower(path[len(path)-1])
 	deepestMap := deepSearch(v.override, path[0:len(path)-1])
 

viper_test.go

@@ -2718,3 +2718,14 @@ func skipWindows(t *testing.T) {
 		t.Skip("Skip test on Windows")
 	}
 }
+
+// Test the Set method with key delimiter for case insenitivty
+func TestUpperCaseKeyDelimiter(t *testing.T) {
+	v := NewWithOptions(KeyDelimiter("Z"))
+	v.Set("fooZbar", "Foo Bar Baz")
+
+	got := v.Get("foo")
+	want := map[string]any{"bar": "Foo Bar Baz"}
+
+	assert.Equal(t, want, got)
+}