Why does the MergeConfigMap method return always nil

[nohkwangsun]

Hi, I'm the begginer of golang and viper.

When I wanted to merge 2 configs into one, I used viper.MergeConfigMap method.
Unfortunately, my configs have a problem related to format differences.
Error log was printed like below.

API server listening at: 127.0.0.1:57055
Using config file: test.yaml
ERROR 2021/10/18 22:32:51 svType != tvType; key=cluster, st=map[string]interface {}, tt=string, sv=map[chart:brigh

And I checked the source code to resovle my issue.
The MergeConfigMap code shows that the method return always nil.
It's not my expectation.
The error log was printed, so I thought of couse the method return error not nil.

func (v *Viper) MergeConfigMap(cfg map[string]interface{}) error {
	if v.config == nil {
		v.config = make(map[string]interface{})
	}
	insensitiviseMap(cfg)
	mergeMaps(cfg, v.config, nil)
	return nil
}

There are any reason that the method return nil ?
If not, can I change some codes and make PR?