Is must that the first alpha of the method name in java interface is upper case to compatible with golang?

**What would you like to be added**:

If apache/dubbo-go project can compatible with golang by comparing to the method name in client.yml. If the first alpha of the method name in the config is not Upper case, transfer it to lower case when searching the java method name.

**Why is this needed**:

I am trying to call java dubbo services by using apache/dubbo-go. Due to historical reasons, it is not possible to change java codes because they are called by other many projects.

Start by tracing how dubbo-go reads the method name from client.yml and resolves the corresponding Java service method. Confirm the existing name-matching behavior with a mixed-case example, then add coverage for a lowercase initial character and verify that Java Dubbo calls still resolve correctly.

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