Refactor : CommandService & MainService

[joyguptaa]

          @pankajjs  and @joyguptaa

for me Looking at above two function signatures, they're syntactically different but functionally similar.
@joyguptaa's code explicitly returns a function with the HTTP handler signature, while @pankajjs your suggestions returns the same function but uses the type alias http.HandlerFunc. so please help me to understand about your suggestions looks like NIT to me

Originally posted by @iamitprakash in #55 (comment)