==> ./pkgb/pkgb.go <==
package pkgb

import "bugtest/pkga"

type B interface{
        GetA() pkga.A
}



==> ./test.go <==
package main

import (
        "bugtest/pkga"
        "bugtest/pkgc"
)

type testA struct {
}

func (testA) Func() {
}

type testB struct {
        a pkga.A
}

func (b testB) GetA() pkga.A {
        return b.a
}
func main() {
        b := testB{testA{}}
        pkgc.Test(b)
}

==> ./pkgc/pkgc.go <==
package pkgc

import (
        "bugtest/pkga"
        "bugtest/pkgb"
)

func test(b pkgb.B, f func(pkga.A)) {
        f(b.GetA())
}

func Test(b pkgb.B) {
        test(b, pkga.A.Func)
}

==> ./pkga/pkga.go <==
package pkga

type A interface {
        Func()
}

==> ./go.mod <==
module bugtest

go 1.14

# bugtest
/usr/bin/ld: /home/zhsj/.cache/go-build/ea/ea4b9775947f0eae0848aa6de3b1dd2e84c3f5cbb5d5164df059bb4d2099acaa-d(_go_.o): in function `bugtest..z2fpkgc.Test':
/tmp/t/tt/ /tmp/t/tt/pkgc/pkgc.go:13: undefined reference to `bugtest..z2fpkgc.bugtest..z2fpkgc..thunk0..f'
collect2: error: ld returned 1 exit status