在同一包中找不到结构

suddenly, vscode cannot get access struct in the same package,but different files.

the error showed undefined struct

Previously vscode was able to instantiate struct across files(vscode+go1.12.4)

the sample code like this:

file1 a.go

package main

import "fmt"

type su struct {
    Sfd string
    Sf  int
}

func (sed *su) do() {
    fmt.Println(sed.Sfd + string(sed.Sf))
}

file2 main.go

package main

import "fmt"

func main() {
    d := su{}
    fmt.Println(d)
}

these two files are in the same package

have some one met the same problem?