Prefix Unexported Globals with _

Prefix unexported top-level vars and consts with _ to make it clear whenthey are used that they are global symbols.

Exception: Unexported error values, which should be prefixed with err.

Rationale: Top-level variables and constants have a package scope. Using ageneric name makes it easy to accidentally use the wrong value in a differentfile.

// foo.go
 
const (
  defaultPort = 8080
  defaultUser = "user"
)
 
// bar.go
 
func Bar() {
  defaultPort := 9090
  …
  fmt.Println("Default port", defaultPort)
 
  // We will not see a compile error if the first line of
  // Bar() is deleted.
}

// foo.go
 
const (
  _defaultPort = 8080
  _defaultUser = "user"
)