// NeedDeps adds the fields requested by the LoadMode in the packages in Imports.

       // NeedDeps causes all Packages transitively reachable through
       // the Imports map to also be populated according to the LoadMode.

xtools$ cat main.go 
package main

import (
	"fmt"
	"log"

	"golang.org/x/tools/go/packages"
)

func main() {
	cfg := &packages.Config{
		Mode: packages.NeedImports |
			packages.NeedCompiledGoFiles |
			//packages.NeedDeps |       // try with and without this line
			0,
	}
	pkgs, err := packages.Load(cfg, "runtime")
	if err != nil {
		log.Fatalf("load: %v", err)
	}
	packages.Visit(pkgs, nil, func(p *packages.Package) {
		fmt.Println(p, len(p.CompiledGoFiles))
	})
}

xtools$ go run  ./main.go  > with
# Now uncomment the NeedDeps line.
xtools$ go run  ./main.go  > without
xtools$ diff with without
xtools$
# nothing