[go-nuts] better way to load config file during unit test?

Hi,

     In my source tree, a 'configs' folder containing all possible config
files, like this:
     - configs
       \ test.json
       \ production.json
     - main.go

     Pseudo code of load config when unit test:
- get the absolute path of the folder containing main.go
   * this can be achieved by utilize runtime.Caller(1)
- join this path when 'configs', and 'test.json'

     It works when the binary is built by the 'main.go' I was editing.
     When unit test, it seems that all source code would be copied to a
temporary folder to build the binary for testing.
     This means the result of runtime.Caller(1) would not be the same as my
expectation.

     Is there any way to make 'go test' to build binary without making a
copy of source code?