godef by expression not working with go/packages

[segevfiner]

I think this works without go/packages:

1. Create hello.go:

package main

import "fmt"

func main() {
	fmt.Println("Hello, World!")
}

2. go mod init.
3. Run godef -f hello.go fmt.Println.
4. You get the error: godef: Offset -1 was not a valid identifier

[sunliver]

try godef -t -f hello.go -o 43, you may get

xxx/hello.go:3:8
import (fmt "fmt")

[segevfiner]

try godef -t -f hello.go -o 43, you may get

xxx/hello.go:3:8
import (fmt "fmt")

This is about the expression mode not working. Offset mode still works.

[sunliver]

Mod is not supporting expression now, it uses https://godoc.org/golang.org/x/tools/go/packages to find definition.