No it does not, Sliggo can only evolve into Goodra by natural rain.
You pretty much have to look for rain on the routes as it constantly changes from route to route
Hope I helped :)
Source: experiance when I tried evolving mine
No, it doesn't
For Sliggo to evolve you need to level it up in natural rain.
This means you can't evolve it by using Rain Dance.
This is both Source and tips and tricks on how to find natural rain (marriland forums)
Hope this helped!