Request params are not getting merged with instance params

Describe the bug

Specific request params do not get merged with the instance default params.

To Reproduce

const instance = axios.create({
    baseURL: "http://www.example.com",
    params: {
      q: "question",
    }
  });

instance.get("/page", 
  { 
    params: { 
      page: 2 
    }
  }
)

What happens is that the request param object overrides the instance default param object. The instance no longer has a query param of q.

Expected behavior

According to the docs, all configuration options are merged. https://github.com/axios/axios#instance-methods

I expected request to contain both q and page params. This is also how it was working in version 0.18.0, which is how I noticed.

Environment:

• Axios Version: 0.19.0
• OS: 10.14.5 (18F132)
• Browser: Node Express, and Chrome
• Browser: Node 10.15.0, Chrome Version 74.0.3729.169 (Official Build) (64-bit)

[nghiepdev]

Waiting for an official fix 😭

[miroshnik]

some kind of endless drama